‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
STORM DRAINAGE
Exception:
Cooling tower blow
-
down shall discharge into the sanitary drainage system.
1104.5 Parkin
g garage floor drains.
Floor drains provided in open or enclosed parking garages shall drain to the 
storm drainage system.
Exception:
Where the storm drainage system discharges to a dedicated storm sewer, parking garage floor drains 
shall be connected to t
he sanitary drainage system.
SECTION PC 1105
ROOF DRAINS
1105.1 
General.
Roof drains shall be installed in accordance with the manufacturer’s instructions. The inside opening 
for the roof drain shall not be obstructed by the roofing membrane material.
1105
.2
Roof drain flow rate. 
The published roof drain flow rate, based on the head of water above the roof drain, 
shall be used to size the storm drainage system in accordance with Section 1106. The flow rate used for sizing the 
storm drainage piping shall be 
based on the maximum anticipated ponding at the roof drain.
SECTION PC 1106
SIZE OF CONDUCTORS, LEADERS AND STORM DRAINS
‡‡‡
1106.1 General. 
The size of the vertical conductors and 
leaders, gutters,
building storm drains, building storm 
sewers and any horizontal branches of such drains or sewers
shall be based on the 100
-
year hourly rainfall rate 
of 3 
inches (76 mm) per hour. Sizing for secondary and combined primary and secondary conductors, leaders
and drains 
shall be in accordance with Section 1108
.
1106.2 Size of storm drain piping. 
Vertical and horizontal storm drain piping shall be sized based on the flow rate 
through the roof drain. The flow rate in storm drain piping shall not exceed that 
specified in Table 1106.2.
TABLE 1106.2
STORM DRAIN PIPE SIZING
PIPE SIZE (inches)
CAPACITY (gpm)
VERTICAL DRAIN
SLOPE OF HORIZONTAL DRAIN
1
/
16
inch per foot
1
/
8
inch per foot
1
/
4
inch per foot
1
/
2
inch per foot
2
34
15
22
31
44
3
87
39
55
79
111
4
180
81
115
163
231
5
311
117
165
234
331
6
538
243
344
487
689
8
1,117
505
714
1,010
1,429
10
2,050
927
1,311
1,855
2,623
12
3,272
1,480
2,093
2,960
4,187
14
4,204
1,312
1,856
2,621
3,713
15
5,543
2,508
3,546
5,016
7,093
STORM DRAINAGE
16
5,543
2,508
3,546
5,016
7,093
18
8.218
3,100
4,386
6,192
8,773
1106.2.1 Values for continuous flow. 
Where there is a continuous or semicontinuous discharge into the building 
storm drain or building storm sewer, such as from a pump, ejector, air conditioning plant or 
similar device, each 
gallon per minute of such discharge shall be computed as being equivalent to 32 square feet (2.97 m
2
) of roof area, 
based on a rainfall rate of 3 inches (75 mm) per hour.
1106.3 Vertical leader sizing. 
Vertical leaders shall be sized b
ased on the flow rate from horizontal gutters or the 
maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 
1106.3.
STORM DRAINAGE
TABLE 1106.3
VERTICAL LEADER SIZING
SIZE OF LEADER
(inches)
CAPACITY
(gpm)
2
30
2 × 2
30
1
1
/
2
× 2
1
/
2
30
2
1
/
2
54
2
1
/
2
× 2
1
/
2
54
3
92
2 × 4
92
2
1
/
2
× 3
92
4
192
3 × 4
1
/
4
192
3
1
/
2
× 4
192
5
360
4 × 5
360
4
1
/
2
× 4
1
/
2
360
6
563
5 × 6
563
5
1
/
2
× 5
1
/
2
563
8
1208
6 × 8
1208
For SI: 1 inch = 25.4 mm, 1 gallon per 
minute = 3.785 L/m.
1106.4 Vertical walls. 
In sizing roof drains and storm drainage piping, one
-
fourth of the area of any vertical wall that 
diverts rainwater to the roof or the setback roof of a building shall be added to the projected roof area for inclu
sion in 
calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Exceptions:
1.
Where vertical conductors or leaders and downstream piping has been sized for secondary roof drainage in 
accordance with Section 1108
, the contribution from vertical walls need not be added to the projected roof 
area.
2.
Section 1106.4 shall not be applicable to vertical walls fronting a public right
-
of
-
way.
1106.5 Parapet wall scupper location. 
Parapet wall roof drainage scupper and overflow scupper location shall com-
ply with the requirements of Section 1503.4 of 
the 
New York City 
Building Code
.
STORM DRAINAGE
1106.6 Size of roof gutters.
Horizontal
gutters shall be sized based on the 
flow rate from the
roof surface. The flow 
rate in horizontal gutters shall not exceed that specified in Table 1106.6.
TABLE 1106.6
HORIZONTAL GUTTER SIZING
GUTTER DIMENSIONS
a
(inches)
SLOPE
(inch per foot)
CAPACITY
(gpm
)
1
1
/
2
× 2
1
/
2
1
/
4
26
1
1
/
2
× 2
1
/
2
1
/
2
40
4
1
/
8
39
2
1
/
4
× 3
1
/
4
55
2
1
/
4
× 3
1
/
2
87
5
1
/
8
74
4 × 2
1
/
2
1
/
4
106
3 × 3
1
/
2
1
/
2
156
6
1
/
8
110
3 × 5
1
/
4
157
3 × 5
1
/
2
225
8
1
/
16
172
8
1
/
8
247
4
1
/
2
× 6
1
/
4
348
4
1
/
2
× 6
1
/
2
494
10
1
/
16
331
10
1
/
8
472
5 × 8
1
/
4
651
4 × 10
1
/
2
1055
For SI:
1 inch = 25.4 mm, 1 foot = 304.8 mm, 
1 gallon per minute = 3.785 L/m, 1 inch per foot = 83.3 mm/m.
a.
Dimensions are width by depth for rectangular shapes. Single dimensions are diameters of a sem
icircle.
SECTION PC 1107
SIPHONIC ROOF DRAINAGE SYSTEMS 
STORM DRAINAGE
1107.1 General. 
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 
and ASPE 45.
SECTION PC 1108
SECONDARY (EMERGENCY) ROOF DRAINS
1108.1 Secondary (emergency overflow) drains or scuppers. 
Where roof drains are required, secondary (emergency 
overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in 
such a manner that water will
be entrapped if the primary drains allow buildup for any reason. 
The inlet elevation of 
secondary (overflow) drains and the invert elevation of overflow scuppers should be not less than 2 inches (51 mm) 
or more than 4 inches (102 mm) above the low point o
f the (adjacent to) roof surface unless a safer water depth 
loading, including the required hydraulic head to maintain required flow rate out of the overflow drainage system 
that has been determined by the structural design. 
Where primary and secondary roo
f drains are manufactured as a 
single assembly, the inlet and outlet for each drain shall be independent.
1108.2 Separate systems required. 
Secondary roof drain systems shall have the end point of discharge separate from 
the primary system. Discharge shall
be above grade, in a location 
that
would normally be observed by the building 
occupants or maintenance personnel
. 
Exception:
Secondary drainage system may tie into the primary drainage system in the vertical conductors 
where 
separate systems are impracti
cal or to prevent water from flowing over sidewalk or pedestrian walkways.
1108.3 Sizing of secondary drains. 
Secondary (emergency) roof drain systems shall be sized in accordance with 
Section 1106 based on the rainfall rate 
of 3 inches (76 mm) per hour
. S
cuppers shall be sized to prevent the depth of 
ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall 
have an opening dimension of not less than 4 inches (102 mm). 
The flow through the primary syst
em shall not be 
considered when sizing the secondary roof drain system.
Exception:
Where secondary drainage systems tie into primary drainage systems, the combined primary and sec-
ondary system shall be sized based on their combined rainfall rate of 6 inche
s (152 mm) per hour.
SECTION PC 1109
COMBINED SANITARY AND STORM 
SYSTEM
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new instal-
lations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable 
requirements of the Department of Environmental Protection. With respect to 
repair of combined systems installed 
prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be com-
puted in accordance with the method in Section 1106. The fixture units shall be converted into an equi
valent pro-
jected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, 
the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m
2
). Where the total 
fixture 
load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square 
feet (0.48 m
2
) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
SECTION PC 1110
CONTROLLED FLOW ROOF DRAIN 
SYSTEMS
1110.1 General. 
The roof of a structure shall be designed for the storage of water where the storm drainage system is 
engineered for controlled flow. The controlled flow roof drain 
system
shall be an engineered system in accordance 
with this sectio
n and Section 
28
-
113.2.2 of the 
Administrative Code
.
The controlled flow system shall be designed 
based on the 
design
rainfall rate in accordance with Section 1106.1.
1110.2 Control devices. 
The control devices shall be installed so that the rate of discha
rge of water per minute shall 
not exceed the values for controlled flow as 
allowed by the Department of Environmental Protection
.
1110.3 Installation. 
Runoff control shall be by control devices. Control devices shall be protected by strainers.
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
STORM DRAINAGE
Exception:
Cooling tower blow
-
down shall discharge into the sanitary drainage system.
1104.5 Parkin
g garage floor drains.
Floor drains provided in open or enclosed parking garages shall drain to the 
storm drainage system.
Exception:
Where the storm drainage system discharges to a dedicated storm sewer, parking garage floor drains 
shall be connected to t
he sanitary drainage system.
SECTION PC 1105
ROOF DRAINS
1105.1 
General.
Roof drains shall be installed in accordance with the manufacturer’s instructions. The inside opening 
for the roof drain shall not be obstructed by the roofing membrane material.
1105
.2
Roof drain flow rate. 
The published roof drain flow rate, based on the head of water above the roof drain, 
shall be used to size the storm drainage system in accordance with Section 1106. The flow rate used for sizing the 
storm drainage piping shall be 
based on the maximum anticipated ponding at the roof drain.
SECTION PC 1106
SIZE OF CONDUCTORS, LEADERS AND STORM DRAINS
‡‡‡
1106.1 General. 
The size of the vertical conductors and 
leaders, gutters,
building storm drains, building storm 
sewers and any horizontal branches of such drains or sewers
shall be based on the 100
-
year hourly rainfall rate 
of 3 
inches (76 mm) per hour. Sizing for secondary and combined primary and secondary conductors, leaders
and drains 
shall be in accordance with Section 1108
.
1106.2 Size of storm drain piping. 
Vertical and horizontal storm drain piping shall be sized based on the flow rate 
through the roof drain. The flow rate in storm drain piping shall not exceed that 
specified in Table 1106.2.
TABLE 1106.2
STORM DRAIN PIPE SIZING
PIPE SIZE (inches)
CAPACITY (gpm)
VERTICAL DRAIN
SLOPE OF HORIZONTAL DRAIN
1
/
16
inch per foot
1
/
8
inch per foot
1
/
4
inch per foot
1
/
2
inch per foot
2
34
15
22
31
44
3
87
39
55
79
111
4
180
81
115
163
231
5
311
117
165
234
331
6
538
243
344
487
689
8
1,117
505
714
1,010
1,429
10
2,050
927
1,311
1,855
2,623
12
3,272
1,480
2,093
2,960
4,187
14
4,204
1,312
1,856
2,621
3,713
15
5,543
2,508
3,546
5,016
7,093
STORM DRAINAGE
16
5,543
2,508
3,546
5,016
7,093
18
8.218
3,100
4,386
6,192
8,773
1106.2.1 Values for continuous flow. 
Where there is a continuous or semicontinuous discharge into the building 
storm drain or building storm sewer, such as from a pump, ejector, air conditioning plant or 
similar device, each 
gallon per minute of such discharge shall be computed as being equivalent to 32 square feet (2.97 m
2
) of roof area, 
based on a rainfall rate of 3 inches (75 mm) per hour.
1106.3 Vertical leader sizing. 
Vertical leaders shall be sized b
ased on the flow rate from horizontal gutters or the 
maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 
1106.3.
STORM DRAINAGE
TABLE 1106.3
VERTICAL LEADER SIZING
SIZE OF LEADER
(inches)
CAPACITY
(gpm)
2
30
2 × 2
30
1
1
/
2
× 2
1
/
2
30
2
1
/
2
54
2
1
/
2
× 2
1
/
2
54
3
92
2 × 4
92
2
1
/
2
× 3
92
4
192
3 × 4
1
/
4
192
3
1
/
2
× 4
192
5
360
4 × 5
360
4
1
/
2
× 4
1
/
2
360
6
563
5 × 6
563
5
1
/
2
× 5
1
/
2
563
8
1208
6 × 8
1208
For SI: 1 inch = 25.4 mm, 1 gallon per 
minute = 3.785 L/m.
1106.4 Vertical walls. 
In sizing roof drains and storm drainage piping, one
-
fourth of the area of any vertical wall that 
diverts rainwater to the roof or the setback roof of a building shall be added to the projected roof area for inclu
sion in 
calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Exceptions:
1.
Where vertical conductors or leaders and downstream piping has been sized for secondary roof drainage in 
accordance with Section 1108
, the contribution from vertical walls need not be added to the projected roof 
area.
2.
Section 1106.4 shall not be applicable to vertical walls fronting a public right
-
of
-
way.
1106.5 Parapet wall scupper location. 
Parapet wall roof drainage scupper and overflow scupper location shall com-
ply with the requirements of Section 1503.4 of 
the 
New York City 
Building Code
.
STORM DRAINAGE
1106.6 Size of roof gutters.
Horizontal
gutters shall be sized based on the 
flow rate from the
roof surface. The flow 
rate in horizontal gutters shall not exceed that specified in Table 1106.6.
TABLE 1106.6
HORIZONTAL GUTTER SIZING
GUTTER DIMENSIONS
a
(inches)
SLOPE
(inch per foot)
CAPACITY
(gpm
)
1
1
/
2
× 2
1
/
2
1
/
4
26
1
1
/
2
× 2
1
/
2
1
/
2
40
4
1
/
8
39
2
1
/
4
× 3
1
/
4
55
2
1
/
4
× 3
1
/
2
87
5
1
/
8
74
4 × 2
1
/
2
1
/
4
106
3 × 3
1
/
2
1
/
2
156
6
1
/
8
110
3 × 5
1
/
4
157
3 × 5
1
/
2
225
8
1
/
16
172
8
1
/
8
247
4
1
/
2
× 6
1
/
4
348
4
1
/
2
× 6
1
/
2
494
10
1
/
16
331
10
1
/
8
472
5 × 8
1
/
4
651
4 × 10
1
/
2
1055
For SI:
1 inch = 25.4 mm, 1 foot = 304.8 mm, 
1 gallon per minute = 3.785 L/m, 1 inch per foot = 83.3 mm/m.
a.
Dimensions are width by depth for rectangular shapes. Single dimensions are diameters of a sem
icircle.
SECTION PC 1107
SIPHONIC ROOF DRAINAGE SYSTEMS 
STORM DRAINAGE
1107.1 General. 
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 
and ASPE 45.
SECTION PC 1108
SECONDARY (EMERGENCY) ROOF DRAINS
1108.1 Secondary (emergency overflow) drains or scuppers. 
Where roof drains are required, secondary (emergency 
overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in 
such a manner that water will
be entrapped if the primary drains allow buildup for any reason. 
The inlet elevation of 
secondary (overflow) drains and the invert elevation of overflow scuppers should be not less than 2 inches (51 mm) 
or more than 4 inches (102 mm) above the low point o
f the (adjacent to) roof surface unless a safer water depth 
loading, including the required hydraulic head to maintain required flow rate out of the overflow drainage system 
that has been determined by the structural design. 
Where primary and secondary roo
f drains are manufactured as a 
single assembly, the inlet and outlet for each drain shall be independent.
1108.2 Separate systems required. 
Secondary roof drain systems shall have the end point of discharge separate from 
the primary system. Discharge shall
be above grade, in a location 
that
would normally be observed by the building 
occupants or maintenance personnel
. 
Exception:
Secondary drainage system may tie into the primary drainage system in the vertical conductors 
where 
separate systems are impracti
cal or to prevent water from flowing over sidewalk or pedestrian walkways.
1108.3 Sizing of secondary drains. 
Secondary (emergency) roof drain systems shall be sized in accordance with 
Section 1106 based on the rainfall rate 
of 3 inches (76 mm) per hour
. S
cuppers shall be sized to prevent the depth of 
ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall 
have an opening dimension of not less than 4 inches (102 mm). 
The flow through the primary syst
em shall not be 
considered when sizing the secondary roof drain system.
Exception:
Where secondary drainage systems tie into primary drainage systems, the combined primary and sec-
ondary system shall be sized based on their combined rainfall rate of 6 inche
s (152 mm) per hour.
SECTION PC 1109
COMBINED SANITARY AND STORM 
SYSTEM
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new instal-
lations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable 
requirements of the Department of Environmental Protection. With respect to 
repair of combined systems installed 
prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be com-
puted in accordance with the method in Section 1106. The fixture units shall be converted into an equi
valent pro-
jected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, 
the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m
2
). Where the total 
fixture 
load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square 
feet (0.48 m
2
) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
SECTION PC 1110
CONTROLLED FLOW ROOF DRAIN 
SYSTEMS
1110.1 General. 
The roof of a structure shall be designed for the storage of water where the storm drainage system is 
engineered for controlled flow. The controlled flow roof drain 
system
shall be an engineered system in accordance 
with this sectio
n and Section 
28
-
113.2.2 of the 
Administrative Code
.
The controlled flow system shall be designed 
based on the 
design
rainfall rate in accordance with Section 1106.1.
1110.2 Control devices. 
The control devices shall be installed so that the rate of discha
rge of water per minute shall 
not exceed the values for controlled flow as 
allowed by the Department of Environmental Protection
.
1110.3 Installation. 
Runoff control shall be by control devices. Control devices shall be protected by strainers.
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
STORM DRAINAGE
Exception:
Cooling tower blow
-
down shall discharge into the sanitary drainage system.
1104.5 Parkin
g garage floor drains.
Floor drains provided in open or enclosed parking garages shall drain to the 
storm drainage system.
Exception:
Where the storm drainage system discharges to a dedicated storm sewer, parking garage floor drains 
shall be connected to t
he sanitary drainage system.
SECTION PC 1105
ROOF DRAINS
1105.1 
General.
Roof drains shall be installed in accordance with the manufacturer’s instructions. The inside opening 
for the roof drain shall not be obstructed by the roofing membrane material.
1105
.2
Roof drain flow rate. 
The published roof drain flow rate, based on the head of water above the roof drain, 
shall be used to size the storm drainage system in accordance with Section 1106. The flow rate used for sizing the 
storm drainage piping shall be 
based on the maximum anticipated ponding at the roof drain.
SECTION PC 1106
SIZE OF CONDUCTORS, LEADERS AND STORM DRAINS
‡‡‡
1106.1 General. 
The size of the vertical conductors and 
leaders, gutters,
building storm drains, building storm 
sewers and any horizontal branches of such drains or sewers
shall be based on the 100
-
year hourly rainfall rate 
of 3 
inches (76 mm) per hour. Sizing for secondary and combined primary and secondary conductors, leaders
and drains 
shall be in accordance with Section 1108
.
1106.2 Size of storm drain piping. 
Vertical and horizontal storm drain piping shall be sized based on the flow rate 
through the roof drain. The flow rate in storm drain piping shall not exceed that 
specified in Table 1106.2.
TABLE 1106.2
STORM DRAIN PIPE SIZING
PIPE SIZE (inches)
CAPACITY (gpm)
VERTICAL DRAIN
SLOPE OF HORIZONTAL DRAIN
1
/
16
inch per foot
1
/
8
inch per foot
1
/
4
inch per foot
1
/
2
inch per foot
2
34
15
22
31
44
3
87
39
55
79
111
4
180
81
115
163
231
5
311
117
165
234
331
6
538
243
344
487
689
8
1,117
505
714
1,010
1,429
10
2,050
927
1,311
1,855
2,623
12
3,272
1,480
2,093
2,960
4,187
14
4,204
1,312
1,856
2,621
3,713
15
5,543
2,508
3,546
5,016
7,093
STORM DRAINAGE
16
5,543
2,508
3,546
5,016
7,093
18
8.218
3,100
4,386
6,192
8,773
1106.2.1 Values for continuous flow. 
Where there is a continuous or semicontinuous discharge into the building 
storm drain or building storm sewer, such as from a pump, ejector, air conditioning plant or 
similar device, each 
gallon per minute of such discharge shall be computed as being equivalent to 32 square feet (2.97 m
2
) of roof area, 
based on a rainfall rate of 3 inches (75 mm) per hour.
1106.3 Vertical leader sizing. 
Vertical leaders shall be sized b
ased on the flow rate from horizontal gutters or the 
maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 
1106.3.
STORM DRAINAGE
TABLE 1106.3
VERTICAL LEADER SIZING
SIZE OF LEADER
(inches)
CAPACITY
(gpm)
2
30
2 × 2
30
1
1
/
2
× 2
1
/
2
30
2
1
/
2
54
2
1
/
2
× 2
1
/
2
54
3
92
2 × 4
92
2
1
/
2
× 3
92
4
192
3 × 4
1
/
4
192
3
1
/
2
× 4
192
5
360
4 × 5
360
4
1
/
2
× 4
1
/
2
360
6
563
5 × 6
563
5
1
/
2
× 5
1
/
2
563
8
1208
6 × 8
1208
For SI: 1 inch = 25.4 mm, 1 gallon per 
minute = 3.785 L/m.
1106.4 Vertical walls. 
In sizing roof drains and storm drainage piping, one
-
fourth of the area of any vertical wall that 
diverts rainwater to the roof or the setback roof of a building shall be added to the projected roof area for inclu
sion in 
calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Exceptions:
1.
Where vertical conductors or leaders and downstream piping has been sized for secondary roof drainage in 
accordance with Section 1108
, the contribution from vertical walls need not be added to the projected roof 
area.
2.
Section 1106.4 shall not be applicable to vertical walls fronting a public right
-
of
-
way.
1106.5 Parapet wall scupper location. 
Parapet wall roof drainage scupper and overflow scupper location shall com-
ply with the requirements of Section 1503.4 of 
the 
New York City 
Building Code
.
STORM DRAINAGE
1106.6 Size of roof gutters.
Horizontal
gutters shall be sized based on the 
flow rate from the
roof surface. The flow 
rate in horizontal gutters shall not exceed that specified in Table 1106.6.
TABLE 1106.6
HORIZONTAL GUTTER SIZING
GUTTER DIMENSIONS
a
(inches)
SLOPE
(inch per foot)
CAPACITY
(gpm
)
1
1
/
2
× 2
1
/
2
1
/
4
26
1
1
/
2
× 2
1
/
2
1
/
2
40
4
1
/
8
39
2
1
/
4
× 3
1
/
4
55
2
1
/
4
× 3
1
/
2
87
5
1
/
8
74
4 × 2
1
/
2
1
/
4
106
3 × 3
1
/
2
1
/
2
156
6
1
/
8
110
3 × 5
1
/
4
157
3 × 5
1
/
2
225
8
1
/
16
172
8
1
/
8
247
4
1
/
2
× 6
1
/
4
348
4
1
/
2
× 6
1
/
2
494
10
1
/
16
331
10
1
/
8
472
5 × 8
1
/
4
651
4 × 10
1
/
2
1055
For SI:
1 inch = 25.4 mm, 1 foot = 304.8 mm, 
1 gallon per minute = 3.785 L/m, 1 inch per foot = 83.3 mm/m.
a.
Dimensions are width by depth for rectangular shapes. Single dimensions are diameters of a sem
icircle.
SECTION PC 1107
SIPHONIC ROOF DRAINAGE SYSTEMS 
STORM DRAINAGE
1107.1 General. 
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 
and ASPE 45.
SECTION PC 1108
SECONDARY (EMERGENCY) ROOF DRAINS
1108.1 Secondary (emergency overflow) drains or scuppers. 
Where roof drains are required, secondary (emergency 
overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in 
such a manner that water will
be entrapped if the primary drains allow buildup for any reason. 
The inlet elevation of 
secondary (overflow) drains and the invert elevation of overflow scuppers should be not less than 2 inches (51 mm) 
or more than 4 inches (102 mm) above the low point o
f the (adjacent to) roof surface unless a safer water depth 
loading, including the required hydraulic head to maintain required flow rate out of the overflow drainage system 
that has been determined by the structural design. 
Where primary and secondary roo
f drains are manufactured as a 
single assembly, the inlet and outlet for each drain shall be independent.
1108.2 Separate systems required. 
Secondary roof drain systems shall have the end point of discharge separate from 
the primary system. Discharge shall
be above grade, in a location 
that
would normally be observed by the building 
occupants or maintenance personnel
. 
Exception:
Secondary drainage system may tie into the primary drainage system in the vertical conductors 
where 
separate systems are impracti
cal or to prevent water from flowing over sidewalk or pedestrian walkways.
1108.3 Sizing of secondary drains. 
Secondary (emergency) roof drain systems shall be sized in accordance with 
Section 1106 based on the rainfall rate 
of 3 inches (76 mm) per hour
. S
cuppers shall be sized to prevent the depth of 
ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall 
have an opening dimension of not less than 4 inches (102 mm). 
The flow through the primary syst
em shall not be 
considered when sizing the secondary roof drain system.
Exception:
Where secondary drainage systems tie into primary drainage systems, the combined primary and sec-
ondary system shall be sized based on their combined rainfall rate of 6 inche
s (152 mm) per hour.
SECTION PC 1109
COMBINED SANITARY AND STORM 
SYSTEM
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new instal-
lations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable 
requirements of the Department of Environmental Protection. With respect to 
repair of combined systems installed 
prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be com-
puted in accordance with the method in Section 1106. The fixture units shall be converted into an equi
valent pro-
jected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, 
the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m
2
). Where the total 
fixture 
load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square 
feet (0.48 m
2
) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
SECTION PC 1110
CONTROLLED FLOW ROOF DRAIN 
SYSTEMS
1110.1 General. 
The roof of a structure shall be designed for the storage of water where the storm drainage system is 
engineered for controlled flow. The controlled flow roof drain 
system
shall be an engineered system in accordance 
with this sectio
n and Section 
28
-
113.2.2 of the 
Administrative Code
.
The controlled flow system shall be designed 
based on the 
design
rainfall rate in accordance with Section 1106.1.
1110.2 Control devices. 
The control devices shall be installed so that the rate of discha
rge of water per minute shall 
not exceed the values for controlled flow as 
allowed by the Department of Environmental Protection
.
1110.3 Installation. 
Runoff control shall be by control devices. Control devices shall be protected by strainers.
STORM DRAINAGE
1110.4 Minim
um number of roof drains. 
Not less than two roof drains shall be installed in roof areas 10,000 square 
feet (929 m
2
) or less and not less than four roof drains shall be installed in roofs over 10,000 square feet (929 m
2
) in 
area.
SECTION 
PC 
1111
SUBSOIL DR
AINS
1111.1 Subsoil drains. 
Subsoil drains 
carrying groundwater 
shall be open
-
jointed, horizontally split or perforated 
pipe conforming to one of the standards listed in Table 1102.5. Such drains shall not be less than 4 inches (102 mm) 
in diameter. Where 
the building is subject to backwater, the subsoil drain shall be protected by an accessibly located 
backwater valve. 
Subsoil drainage discharged into a public sewer shall be approved by the Department of Environ-
mental Protection. The subsoil
drains
shall discharge into a readily accessible silt and sand interceptor before being 
connected into the gravity drainage or sump system. Subsoil drainage 
shall discharge to a trapped area drain, sump, 
dry well or approved location above ground. The subsoil su
mp shall not be required to have either a gas
-
tight cover 
or a vent. The sump and pumping system shall comply with Section 1113.1.
SECTION 
PC 
1112
BUILDING SUBDRAINS
1112.1 Building subdrains. 
Building subdrains located below the public sewer level shall d
ischarge into a sump or 
receiving tank, the contents of which shall be automatically lifted and discharged into the drainage system as required 
for building sumps. The sump and pumping equipment shall comply with Section 1113.1.
SECTION 
PC 
1113
SUMPS AND P
UMPING SYSTEMS
1113.1 Pumping system. 
The sump pump, pit and discharge piping shall conform to Sections 1113.1.1 through 
1113.1.4.
1113.1.1 Pump capacity and head. 
The sump pump shall be of a capacity and head appropriate to anticipated use 
requirements.
1
113.1.2 Sump pit. 
The sump pit shall be not less than 18 inches (457 mm) in diameter and not less than 24 inches 
(610 mm) 
in depth
, unless otherwise approved. The pit shall be accessible and located such that all drainage flows 
into the pit by gravity. The
sump pit shall be constructed of tile, steel, plastic, cast iron, concrete or other approved 
material, with a removable cover adequate to support anticipated loads in the area of use. The pit floor shall be 
solid and provide permanent support for the pump
.
1113.1.3 Electrical. 
Electrical service outlets, when required, shall meet the requirements of 
the 
New York City 
Electrical Code
.
1113.1.4 Piping. 
Discharge piping shall meet the requirements of Section 1102.2, 1102.3 or 1102.4 and shall in-
clude a gate v
alve and a full flow check valve. Pipe and fittings shall be the same size as, or larger than, the pump 
discharge 
tapping.
Exception: 
In one
-
and two
-
family dwellings, only a check valve shall be required, located on the discharge 
piping from the pump or e
jector.
SECTION PC 1114
PRIVATE ON
-
SITE STORMWATER DISPOSAL SYSTEMS
1114.1 General.
Private on
-
site stormwater disposal systems shall comply with the provisions of Section 1114.
1114.1.1 When permitted.
The use of private on
-
site stormwater disposal system
s shall be permitted only in the 
following circumstances:
STORM DRAINAGE
1.
Pursuant to a certification issued by the New York City Department of Environmental Protection that a public 
storm or combined sewer is not available or that connection thereto is not feasible in accordance with Section 
107.6.2.2, Item 1(i);
2.
Pursuant to
a certification submitted by the applicant to the New York City Department of Environmental 
Protection that a public storm or combined sewer is not available or that connection thereto is not feasible, 
in such cases where the availability and feasibility 
of connection to a public storm or combined sewer are 
allowed to be certified by the applicant pursuant to rules of the New York City Department of Environmental 
Protection, in accordance with Section 107.6.2.2, Item 1(ii);
3.
Pursuant to a certification s
ubmitted by the applicant to the New York City Department of Environmental 
Protection authorizing on
-
site stormwater disposal in accordance with Section 107.6.2.1, Item 1;
4.
For enlargements less than 1000 square feet (93 m
2
) in accordance with Section 107.6.2, Exception 2;
5.
For outdoor drinking fountains; or
6.
The disposal of foundation drainage as described in Section 1807.4.3 of the 
New York City Building Code
.
1114.1.2 Acceptable systems.
Acceptable on
-
site stormwater 
disposal systems shall include:
1.
Drywells;
2.
Gravel beds;
3.
Perforated pipe;
4.
Stormwater chambers that facilitate infiltration; and
5.
Alternate method of on
-
site disposal as approved by the department and the New York City Department of 
Environmenta
l Protection.
1114.1.3 Minimum setbacks.
On
-
site stormwater disposal systems shall be located at least 5 feet (1524 mm) from 
all lot lines except where the lot line abuts a public right of way and 10 feet (3048 mm) from all foundations or 
walls existing on
the date of application for a building permit or proposed under the application to construct the 
on
-
site stormwater disposal system. Systems shall be located 20 feet (6096 mm) from disposal fields and 20 feet 
(6096 mm) from seepage pits. On
-
site stormwate
r disposal systems shall not be located within the building foot-
print.
1114.2 Field investigation.
The size of an on
-
site stormwater disposal system shall be predicated on a field investi-
gation performed prior to construction document approval that is perf
ormed at the site of a proposed on
-
site storm-
water disposal system to assess the suitability of the soil and site. The investigation shall conform to Sections 1114.2.1 
and 1114.2.2 and shall occur prior to approval of construction documents for the system.
The field investigation shall 
be subject to special inspection in accordance with Section 1704.21 of the 
New York City Building Code
.
‡‡‡
1114.2.1 Classification of soil based on borings and test pits.
At least one boring and one test pit shall be 
made at
the approximate site of each proposed on
-
site stormwater disposal system. Soil borings and sampling 
procedures shall in accordance with ASTM D 1586 and ASTM D 1587, and generally accepted engineering prac-
tice. Soil and rock samples shall be classified in 
accordance with Section 1802.3 of the 
New York City Building 
Code
.
1114.2.2 Soil infiltration capabilities.
The suitability of the subsurface soils must be verified in place by either a 
percolation test or a permeability test. Where testing determines that
the infiltration rate of the subsurface soils is 
less than 
1
/
2
inch (12.7 mm) per hour, private on
-
site stormwater disposal systems shall not be permitted. Such tests 
shall conform to Section 1114.2.2.1 or 1114.2.2.2, as applicable.
1114.2.2.1 Percolation
tests and procedures.
The infiltration rate of subsurface soils shall be verified with a 
percolation test. Percolation tests shall be performed in accordance with Sections 1114.2.2.1.1 through 
1114.2.2.1.3 under the supervision of a special inspection age
ncy in accordance with Section 1704.21.1 of the 
New York City Building Code
. At least one percolation test in each system area shall be conducted. The holes 
shall be spaced uniformly in relation to the bottom depth of the proposed absorption system. More p
ercolation  of the 
New York City Building Code
.
‡‡‡
1114.2.1 Classification of soil based on borings and test pits.
At least one boring and one test pit shall be 
made at
the approximate site of each proposed on
-
site stormwater disposal system. Soil borings and sampling 
procedures shall in accordance with ASTM D 1586 and ASTM D 1587, and generally accepted engineering prac-
tice. Soil and rock samples shall be classified in 
accordance with Section 1802.3 of the 
New York City Building 
Code
.
1114.2.2 Soil infiltration capabilities.
The suitability of the subsurface soils must be verified in place by either a 
percolation test or a permeability test. Where testing determines that
the infiltration rate of the subsurface soils is 
less than 
1
/
2
inch (12.7 mm) per hour, private on
-
site stormwater disposal systems shall not be permitted. Such tests 
shall conform to Section 1114.2.2.1 or 1114.2.2.2, as applicable.
1114.2.2.1 Percolation
tests and procedures.
The infiltration rate of subsurface soils shall be verified with a 
percolation test. Percolation tests shall be performed in accordance with Sections 1114.2.2.1.1 through 
1114.2.2.1.3 under the supervision of a special inspection age
ncy in accordance with Section 1704.21.1 of the 
New York City Building Code
. At least one percolation test in each system area shall be conducted. The holes 
shall be spaced uniformly in relation to the bottom depth of the proposed absorption system. More p
ercolation 
STORM DRAINAGE
tests shall be made where necessary, depending on system design. The results of the percolation tests shall be 
filed with the department stating the suitability of the site and the capacity of the subsoil for the proposed use.
1114.2.2.1.1 Perco
lation test hole.
The test hole shall be dug or bored. The test hole shall have vertical sides 
and a horizontal dimension of 4 inches to 8 inches (102 mm to 203 mm). The bottom and sides of the hole 
shall be scratched with a sharp
-
pointed instrument to exp
ose the natural soil. All loose material shall be 
removed from the hole and the bottom shall be covered with 2 inches (51 mm) of gravel or coarse sand.
1114.
2.2.1.2 Test procedure, sandy soils.
The hole shall be filled with clear water to a minimum of 12 
inches (305 mm) above the bottom of the hole for tests in sandy soils. The time for this amount of water to 
seep away shall be determined, and this procedure shall be repeated if the water from 
the second filling of 
the hole seeps away in 10 minutes or less. The test shall proceed as follows: Water shall be added to a point 
not more than 6 inches (152 mm) above the gravel or coarse sand. Thereupon, from a fixed reference point, 
water levels shall
be measured at 10
-
minute intervals for a period of 1 hour. Where 6 inches (152 mm) of 
water seeps away in less than 10 minutes, a shorter interval between measurements shall be used, but in no 
case shall the water depth exceed 6 inches (152 mm). Where 6 i
nches (152 mm) of water seeps away in less 
than 2 minutes, the test shall be stopped and a rate of less than 3 minutes per inch (7.2 s/mm) shall be reported. 
The final water level drop shall be used to calculate the percolation rate. Soils not meeting the 
above require-
ments shall be tested in accordance with Section 1114.2.2.1.3.
1114.
2.2.1.3 Test procedure, other soils.
The hole shall be filled with clear water, and a minimum water 
depth of 12 inches (305 mm) shall be maintained above the bottom of the hol
d for a 4
-
hour period by refilling 
whenever necessary or by use of an automatic siphon. Water remaining in the hole after 4 hours shall not be 
removed. Thereafter, the soil shall be allowed to swell not less than 16 hours or more than 30 hours. Imme-
diately
after the soil swelling period, the measurements for determining the percolation rate shall be made as 
follows: Any soil sloughed into the hole shall be removed and the water level shall be adjusted to 6 inches 
(152 mm) above the gravel or coarse sand. Th
ereupon, from a fixed reference point, the water level shall be 
measured at 30
-
minute intervals for a period of 4 hours, unless two successive water level drops do not vary 
by more than 
1
/
16
inch (1.59 mm). At least three water level drops shall be observe
d and recorded. The hole 
shall be filled with clear water to a point not more than 6 inches (152 mm) above the gravel or coarse sand 
whenever it becomes nearly empty. Adjustments of the water level shall not be made during the three meas-
urement periods exc
ept to the limits of the last measured water level drop. When the first 6 inches (152 mm) 
of water seeps away in less than 30 minutes, the time interval between measurements shall be 10 minutes 
and the test run for 1 hour. The water depth shall not exceed 
5 inches (127 mm) at any time during the 
measurement period. The drop that occurs during the final measurement period shall be used in calculating 
the percolation rate.
1114.2.2.2 Permeability tests.
Soil shall be evaluated for estimated percolation based 
on a permeability test 
performed in place, in accordance with procedures established by the New York City Department of Environ-
mental Protection and accepted engineering practice.
1114.3 Design.
The design of on
-
site stormwater disposal systems shall compl
y with the provisions of Section 
1114.3.1.
‡‡‡
1114.3.1 Runoff rate.
The runoff rate shall be calculated using the rational method, Equation 11
-
1. The cal-
culation shall incorporate the total site area with a rainfall intensity value of 
I
= 5.95 inches per 
hour. The weighted 
runoff coefficient shall be calculated using Equation 11
-
2 and shall incorporate the different combinations of sur-
faces using the 
C
values listed below.
Q
= 
C
w
× 
I
× 
A
(Equation 11
-
1)
Where: 
Q
=
developed flow, cubic feet per second 
C
w
=
weighted runoff coefficient 
I
=
the rainfall intensity value, 5.95 in/hr 
A
=
the total site area, acres (ac) 
C
w
=(1/
A
)
∑
(
A
K
×
C
K
)            
(
Equation 11
-
2)
STORM DRAINAGE
Where: 
C
w
= 
weighted runoff coefficient 
A
= 
The total site area, acres (ac) 
A
K
= 
The area of each surface coverage type, acres (ac)
C
K
= 
The runoff coefficient associated with each surface coverage type 
The following 
C
-
values shall be used for calculating a s
ite’s weighted runoff coefficient:
0.95
= 
roof/concrete
0.85
= 
asphalt
0.7 
= 
porous asphalt/concrete or permeable pavers
0.7 
= 
green roof with four or more inches of growing media
0.65
= 
gravel parking lot
0.3 
= 
undeveloped areas
0.2 
= 
gr
ass areas
0.2 
= 
rain gardens, vegetated swales and other surface green infrastructure practices
1114.3.1.1 Storage volume.
The storage volume of an on
-
site stormwater disposal system shall be measured 3 
feet (610 mm) above the level of the water table. The location of the water table shall be verified at the time of 
the field investigation conducted in accordance with Section
1114.2. Unless otherwise approved by the New 
York City Department of Environmental Protection, the storage volume of the on
-
site stormwater disposal sys-
tem shall accommodate the total stormwater volume calculated in this section. The stormwater volume sha
ll be 
calculated as follows:
1.
Compute the runoff rate using Equations 11
-
1 and 11
-
2.
2.
Calculate the outflow rate due to infiltration, in cubic feet per second, using Equation 11
-
3.
3.
Calculate the outflow rate, in cubic feet per second per acre, of im
perviousness using Equation 11
-
4.
4.
Calculate the duration of the design storm in minutes using Equation 11
-
5.
5.
Calculate the maximum required retention volume using Equation 11
-
6.
Q
inf
= (
FA
min
× 
i
soil
)/43,200
(Equation 11
-
3)
where:
Q
inf
=
outflow rate due to infiltration in cubic feet per second
FA
min
=
minimum footprint or surface area of the stormwater disposal system
i
soil
=
soil infiltration rate in inches per hour
Q
o
= 
C
WT
× 
i
× 
A
T
(Equation 11
-
4)
where:
Q
o
=
the 
average outflow rate in cubic feet per second during the rainfall event
C
WT
=
the weighted runoff coefficient for the tributary area
i
=
the average rainfall intensity in inches per hour for the event
A
T
=
the area tributary to the detention facility in a
cres
t
v
= 0.27 × (C
WT
× A
t
/Q
DRR
)
0.5
–
15
(Equation 11
-
5)
where:
t
v
=
the duration of the storm in minutes, with a 10 year
return frequency, requiring the maximum deten-
tion volume with a variable outflow
STORM DRAINAGE
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
Q
DRR
=
the detention f
acility maximum release rate in cubic feet per second
V
v
= (0.19 × C
WT
× At/(t
v
+ 15) 
–
40 × Q
DRR
) × t
v
(
Equation 11
-
6)
where:
V
V
=
the maximum required detention volume in cubic feet with a variable outflow 
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
t
v
=
the duration of the storm in minutes, with a 10 year return frequency, requiring the maximum deten-
tion volume with a variable outflow
Q
DRR
=
the detention facility maximum release rate in cubic feet per second
1114.4 Required components.
On
-
site stormwater
disposal systems shall be designed to provide adequate storage, 
support the use at the surface, and allow for operation and required maintenance. Systems shall be constructed with 
all necessary components and materials required by the manufacturers specif
ications. Drywell design shall incorporate 
a grit chamber, and where required, a sand column constructed in accordance with Figures 1114.4(1) and 1114.4(2), 
respectively.
STORM DRAINAGE
Figure 1114.4(1)
Grit Chamber
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
STORM DRAINAGE
Exception:
Cooling tower blow
-
down shall discharge into the sanitary drainage system.
1104.5 Parkin
g garage floor drains.
Floor drains provided in open or enclosed parking garages shall drain to the 
storm drainage system.
Exception:
Where the storm drainage system discharges to a dedicated storm sewer, parking garage floor drains 
shall be connected to t
he sanitary drainage system.
SECTION PC 1105
ROOF DRAINS
1105.1 
General.
Roof drains shall be installed in accordance with the manufacturer’s instructions. The inside opening 
for the roof drain shall not be obstructed by the roofing membrane material.
1105
.2
Roof drain flow rate. 
The published roof drain flow rate, based on the head of water above the roof drain, 
shall be used to size the storm drainage system in accordance with Section 1106. The flow rate used for sizing the 
storm drainage piping shall be 
based on the maximum anticipated ponding at the roof drain.
SECTION PC 1106
SIZE OF CONDUCTORS, LEADERS AND STORM DRAINS
‡‡‡
1106.1 General. 
The size of the vertical conductors and 
leaders, gutters,
building storm drains, building storm 
sewers and any horizontal branches of such drains or sewers
shall be based on the 100
-
year hourly rainfall rate 
of 3 
inches (76 mm) per hour. Sizing for secondary and combined primary and secondary conductors, leaders
and drains 
shall be in accordance with Section 1108
.
1106.2 Size of storm drain piping. 
Vertical and horizontal storm drain piping shall be sized based on the flow rate 
through the roof drain. The flow rate in storm drain piping shall not exceed that 
specified in Table 1106.2.
TABLE 1106.2
STORM DRAIN PIPE SIZING
PIPE SIZE (inches)
CAPACITY (gpm)
VERTICAL DRAIN
SLOPE OF HORIZONTAL DRAIN
1
/
16
inch per foot
1
/
8
inch per foot
1
/
4
inch per foot
1
/
2
inch per foot
2
34
15
22
31
44
3
87
39
55
79
111
4
180
81
115
163
231
5
311
117
165
234
331
6
538
243
344
487
689
8
1,117
505
714
1,010
1,429
10
2,050
927
1,311
1,855
2,623
12
3,272
1,480
2,093
2,960
4,187
14
4,204
1,312
1,856
2,621
3,713
15
5,543
2,508
3,546
5,016
7,093
STORM DRAINAGE
16
5,543
2,508
3,546
5,016
7,093
18
8.218
3,100
4,386
6,192
8,773
1106.2.1 Values for continuous flow. 
Where there is a continuous or semicontinuous discharge into the building 
storm drain or building storm sewer, such as from a pump, ejector, air conditioning plant or 
similar device, each 
gallon per minute of such discharge shall be computed as being equivalent to 32 square feet (2.97 m
2
) of roof area, 
based on a rainfall rate of 3 inches (75 mm) per hour.
1106.3 Vertical leader sizing. 
Vertical leaders shall be sized b
ased on the flow rate from horizontal gutters or the 
maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 
1106.3.
STORM DRAINAGE
TABLE 1106.3
VERTICAL LEADER SIZING
SIZE OF LEADER
(inches)
CAPACITY
(gpm)
2
30
2 × 2
30
1
1
/
2
× 2
1
/
2
30
2
1
/
2
54
2
1
/
2
× 2
1
/
2
54
3
92
2 × 4
92
2
1
/
2
× 3
92
4
192
3 × 4
1
/
4
192
3
1
/
2
× 4
192
5
360
4 × 5
360
4
1
/
2
× 4
1
/
2
360
6
563
5 × 6
563
5
1
/
2
× 5
1
/
2
563
8
1208
6 × 8
1208
For SI: 1 inch = 25.4 mm, 1 gallon per 
minute = 3.785 L/m.
1106.4 Vertical walls. 
In sizing roof drains and storm drainage piping, one
-
fourth of the area of any vertical wall that 
diverts rainwater to the roof or the setback roof of a building shall be added to the projected roof area for inclu
sion in 
calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Exceptions:
1.
Where vertical conductors or leaders and downstream piping has been sized for secondary roof drainage in 
accordance with Section 1108
, the contribution from vertical walls need not be added to the projected roof 
area.
2.
Section 1106.4 shall not be applicable to vertical walls fronting a public right
-
of
-
way.
1106.5 Parapet wall scupper location. 
Parapet wall roof drainage scupper and overflow scupper location shall com-
ply with the requirements of Section 1503.4 of 
the 
New York City 
Building Code
.
STORM DRAINAGE
1106.6 Size of roof gutters.
Horizontal
gutters shall be sized based on the 
flow rate from the
roof surface. The flow 
rate in horizontal gutters shall not exceed that specified in Table 1106.6.
TABLE 1106.6
HORIZONTAL GUTTER SIZING
GUTTER DIMENSIONS
a
(inches)
SLOPE
(inch per foot)
CAPACITY
(gpm
)
1
1
/
2
× 2
1
/
2
1
/
4
26
1
1
/
2
× 2
1
/
2
1
/
2
40
4
1
/
8
39
2
1
/
4
× 3
1
/
4
55
2
1
/
4
× 3
1
/
2
87
5
1
/
8
74
4 × 2
1
/
2
1
/
4
106
3 × 3
1
/
2
1
/
2
156
6
1
/
8
110
3 × 5
1
/
4
157
3 × 5
1
/
2
225
8
1
/
16
172
8
1
/
8
247
4
1
/
2
× 6
1
/
4
348
4
1
/
2
× 6
1
/
2
494
10
1
/
16
331
10
1
/
8
472
5 × 8
1
/
4
651
4 × 10
1
/
2
1055
For SI:
1 inch = 25.4 mm, 1 foot = 304.8 mm, 
1 gallon per minute = 3.785 L/m, 1 inch per foot = 83.3 mm/m.
a.
Dimensions are width by depth for rectangular shapes. Single dimensions are diameters of a sem
icircle.
SECTION PC 1107
SIPHONIC ROOF DRAINAGE SYSTEMS 
STORM DRAINAGE
1107.1 General. 
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 
and ASPE 45.
SECTION PC 1108
SECONDARY (EMERGENCY) ROOF DRAINS
1108.1 Secondary (emergency overflow) drains or scuppers. 
Where roof drains are required, secondary (emergency 
overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in 
such a manner that water will
be entrapped if the primary drains allow buildup for any reason. 
The inlet elevation of 
secondary (overflow) drains and the invert elevation of overflow scuppers should be not less than 2 inches (51 mm) 
or more than 4 inches (102 mm) above the low point o
f the (adjacent to) roof surface unless a safer water depth 
loading, including the required hydraulic head to maintain required flow rate out of the overflow drainage system 
that has been determined by the structural design. 
Where primary and secondary roo
f drains are manufactured as a 
single assembly, the inlet and outlet for each drain shall be independent.
1108.2 Separate systems required. 
Secondary roof drain systems shall have the end point of discharge separate from 
the primary system. Discharge shall
be above grade, in a location 
that
would normally be observed by the building 
occupants or maintenance personnel
. 
Exception:
Secondary drainage system may tie into the primary drainage system in the vertical conductors 
where 
separate systems are impracti
cal or to prevent water from flowing over sidewalk or pedestrian walkways.
1108.3 Sizing of secondary drains. 
Secondary (emergency) roof drain systems shall be sized in accordance with 
Section 1106 based on the rainfall rate 
of 3 inches (76 mm) per hour
. S
cuppers shall be sized to prevent the depth of 
ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall 
have an opening dimension of not less than 4 inches (102 mm). 
The flow through the primary syst
em shall not be 
considered when sizing the secondary roof drain system.
Exception:
Where secondary drainage systems tie into primary drainage systems, the combined primary and sec-
ondary system shall be sized based on their combined rainfall rate of 6 inche
s (152 mm) per hour.
SECTION PC 1109
COMBINED SANITARY AND STORM 
SYSTEM
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new instal-
lations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable 
requirements of the Department of Environmental Protection. With respect to 
repair of combined systems installed 
prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be com-
puted in accordance with the method in Section 1106. The fixture units shall be converted into an equi
valent pro-
jected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, 
the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m
2
). Where the total 
fixture 
load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square 
feet (0.48 m
2
) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
SECTION PC 1110
CONTROLLED FLOW ROOF DRAIN 
SYSTEMS
1110.1 General. 
The roof of a structure shall be designed for the storage of water where the storm drainage system is 
engineered for controlled flow. The controlled flow roof drain 
system
shall be an engineered system in accordance 
with this sectio
n and Section 
28
-
113.2.2 of the 
Administrative Code
.
The controlled flow system shall be designed 
based on the 
design
rainfall rate in accordance with Section 1106.1.
1110.2 Control devices. 
The control devices shall be installed so that the rate of discha
rge of water per minute shall 
not exceed the values for controlled flow as 
allowed by the Department of Environmental Protection
.
1110.3 Installation. 
Runoff control shall be by control devices. Control devices shall be protected by strainers.
STORM DRAINAGE
1110.4 Minim
um number of roof drains. 
Not less than two roof drains shall be installed in roof areas 10,000 square 
feet (929 m
2
) or less and not less than four roof drains shall be installed in roofs over 10,000 square feet (929 m
2
) in 
area.
SECTION 
PC 
1111
SUBSOIL DR
AINS
1111.1 Subsoil drains. 
Subsoil drains 
carrying groundwater 
shall be open
-
jointed, horizontally split or perforated 
pipe conforming to one of the standards listed in Table 1102.5. Such drains shall not be less than 4 inches (102 mm) 
in diameter. Where 
the building is subject to backwater, the subsoil drain shall be protected by an accessibly located 
backwater valve. 
Subsoil drainage discharged into a public sewer shall be approved by the Department of Environ-
mental Protection. The subsoil
drains
shall discharge into a readily accessible silt and sand interceptor before being 
connected into the gravity drainage or sump system. Subsoil drainage 
shall discharge to a trapped area drain, sump, 
dry well or approved location above ground. The subsoil su
mp shall not be required to have either a gas
-
tight cover 
or a vent. The sump and pumping system shall comply with Section 1113.1.
SECTION 
PC 
1112
BUILDING SUBDRAINS
1112.1 Building subdrains. 
Building subdrains located below the public sewer level shall d
ischarge into a sump or 
receiving tank, the contents of which shall be automatically lifted and discharged into the drainage system as required 
for building sumps. The sump and pumping equipment shall comply with Section 1113.1.
SECTION 
PC 
1113
SUMPS AND P
UMPING SYSTEMS
1113.1 Pumping system. 
The sump pump, pit and discharge piping shall conform to Sections 1113.1.1 through 
1113.1.4.
1113.1.1 Pump capacity and head. 
The sump pump shall be of a capacity and head appropriate to anticipated use 
requirements.
1
113.1.2 Sump pit. 
The sump pit shall be not less than 18 inches (457 mm) in diameter and not less than 24 inches 
(610 mm) 
in depth
, unless otherwise approved. The pit shall be accessible and located such that all drainage flows 
into the pit by gravity. The
sump pit shall be constructed of tile, steel, plastic, cast iron, concrete or other approved 
material, with a removable cover adequate to support anticipated loads in the area of use. The pit floor shall be 
solid and provide permanent support for the pump
.
1113.1.3 Electrical. 
Electrical service outlets, when required, shall meet the requirements of 
the 
New York City 
Electrical Code
.
1113.1.4 Piping. 
Discharge piping shall meet the requirements of Section 1102.2, 1102.3 or 1102.4 and shall in-
clude a gate v
alve and a full flow check valve. Pipe and fittings shall be the same size as, or larger than, the pump 
discharge 
tapping.
Exception: 
In one
-
and two
-
family dwellings, only a check valve shall be required, located on the discharge 
piping from the pump or e
jector.
SECTION PC 1114
PRIVATE ON
-
SITE STORMWATER DISPOSAL SYSTEMS
1114.1 General.
Private on
-
site stormwater disposal systems shall comply with the provisions of Section 1114.
1114.1.1 When permitted.
The use of private on
-
site stormwater disposal system
s shall be permitted only in the 
following circumstances:
STORM DRAINAGE
1.
Pursuant to a certification issued by the New York City Department of Environmental Protection that a public 
storm or combined sewer is not available or that connection thereto is not feasible in accordance with Section 
107.6.2.2, Item 1(i);
2.
Pursuant to
a certification submitted by the applicant to the New York City Department of Environmental 
Protection that a public storm or combined sewer is not available or that connection thereto is not feasible, 
in such cases where the availability and feasibility 
of connection to a public storm or combined sewer are 
allowed to be certified by the applicant pursuant to rules of the New York City Department of Environmental 
Protection, in accordance with Section 107.6.2.2, Item 1(ii);
3.
Pursuant to a certification s
ubmitted by the applicant to the New York City Department of Environmental 
Protection authorizing on
-
site stormwater disposal in accordance with Section 107.6.2.1, Item 1;
4.
For enlargements less than 1000 square feet (93 m
2
) in accordance with Section 107.6.2, Exception 2;
5.
For outdoor drinking fountains; or
6.
The disposal of foundation drainage as described in Section 1807.4.3 of the 
New York City Building Code
.
1114.1.2 Acceptable systems.
Acceptable on
-
site stormwater 
disposal systems shall include:
1.
Drywells;
2.
Gravel beds;
3.
Perforated pipe;
4.
Stormwater chambers that facilitate infiltration; and
5.
Alternate method of on
-
site disposal as approved by the department and the New York City Department of 
Environmenta
l Protection.
1114.1.3 Minimum setbacks.
On
-
site stormwater disposal systems shall be located at least 5 feet (1524 mm) from 
all lot lines except where the lot line abuts a public right of way and 10 feet (3048 mm) from all foundations or 
walls existing on
the date of application for a building permit or proposed under the application to construct the 
on
-
site stormwater disposal system. Systems shall be located 20 feet (6096 mm) from disposal fields and 20 feet 
(6096 mm) from seepage pits. On
-
site stormwate
r disposal systems shall not be located within the building foot-
print.
1114.2 Field investigation.
The size of an on
-
site stormwater disposal system shall be predicated on a field investi-
gation performed prior to construction document approval that is perf
ormed at the site of a proposed on
-
site storm-
water disposal system to assess the suitability of the soil and site. The investigation shall conform to Sections 1114.2.1 
and 1114.2.2 and shall occur prior to approval of construction documents for the system.
The field investigation shall 
be subject to special inspection in accordance with Section 1704.21 of the 
New York City Building Code
.
‡‡‡
1114.2.1 Classification of soil based on borings and test pits.
At least one boring and one test pit shall be 
made at
the approximate site of each proposed on
-
site stormwater disposal system. Soil borings and sampling 
procedures shall in accordance with ASTM D 1586 and ASTM D 1587, and generally accepted engineering prac-
tice. Soil and rock samples shall be classified in 
accordance with Section 1802.3 of the 
New York City Building 
Code
.
1114.2.2 Soil infiltration capabilities.
The suitability of the subsurface soils must be verified in place by either a 
percolation test or a permeability test. Where testing determines that
the infiltration rate of the subsurface soils is 
less than 
1
/
2
inch (12.7 mm) per hour, private on
-
site stormwater disposal systems shall not be permitted. Such tests 
shall conform to Section 1114.2.2.1 or 1114.2.2.2, as applicable.
1114.2.2.1 Percolation
tests and procedures.
The infiltration rate of subsurface soils shall be verified with a 
percolation test. Percolation tests shall be performed in accordance with Sections 1114.2.2.1.1 through 
1114.2.2.1.3 under the supervision of a special inspection age
ncy in accordance with Section 1704.21.1 of the 
New York City Building Code
. At least one percolation test in each system area shall be conducted. The holes 
shall be spaced uniformly in relation to the bottom depth of the proposed absorption system. More p
ercolation 
STORM DRAINAGE
tests shall be made where necessary, depending on system design. The results of the percolation tests shall be 
filed with the department stating the suitability of the site and the capacity of the subsoil for the proposed use.
1114.2.2.1.1 Perco
lation test hole.
The test hole shall be dug or bored. The test hole shall have vertical sides 
and a horizontal dimension of 4 inches to 8 inches (102 mm to 203 mm). The bottom and sides of the hole 
shall be scratched with a sharp
-
pointed instrument to exp
ose the natural soil. All loose material shall be 
removed from the hole and the bottom shall be covered with 2 inches (51 mm) of gravel or coarse sand.
1114.
2.2.1.2 Test procedure, sandy soils.
The hole shall be filled with clear water to a minimum of 12 
inches (305 mm) above the bottom of the hole for tests in sandy soils. The time for this amount of water to 
seep away shall be determined, and this procedure shall be repeated if the water from 
the second filling of 
the hole seeps away in 10 minutes or less. The test shall proceed as follows: Water shall be added to a point 
not more than 6 inches (152 mm) above the gravel or coarse sand. Thereupon, from a fixed reference point, 
water levels shall
be measured at 10
-
minute intervals for a period of 1 hour. Where 6 inches (152 mm) of 
water seeps away in less than 10 minutes, a shorter interval between measurements shall be used, but in no 
case shall the water depth exceed 6 inches (152 mm). Where 6 i
nches (152 mm) of water seeps away in less 
than 2 minutes, the test shall be stopped and a rate of less than 3 minutes per inch (7.2 s/mm) shall be reported. 
The final water level drop shall be used to calculate the percolation rate. Soils not meeting the 
above require-
ments shall be tested in accordance with Section 1114.2.2.1.3.
1114.
2.2.1.3 Test procedure, other soils.
The hole shall be filled with clear water, and a minimum water 
depth of 12 inches (305 mm) shall be maintained above the bottom of the hol
d for a 4
-
hour period by refilling 
whenever necessary or by use of an automatic siphon. Water remaining in the hole after 4 hours shall not be 
removed. Thereafter, the soil shall be allowed to swell not less than 16 hours or more than 30 hours. Imme-
diately
after the soil swelling period, the measurements for determining the percolation rate shall be made as 
follows: Any soil sloughed into the hole shall be removed and the water level shall be adjusted to 6 inches 
(152 mm) above the gravel or coarse sand. Th
ereupon, from a fixed reference point, the water level shall be 
measured at 30
-
minute intervals for a period of 4 hours, unless two successive water level drops do not vary 
by more than 
1
/
16
inch (1.59 mm). At least three water level drops shall be observe
d and recorded. The hole 
shall be filled with clear water to a point not more than 6 inches (152 mm) above the gravel or coarse sand 
whenever it becomes nearly empty. Adjustments of the water level shall not be made during the three meas-
urement periods exc
ept to the limits of the last measured water level drop. When the first 6 inches (152 mm) 
of water seeps away in less than 30 minutes, the time interval between measurements shall be 10 minutes 
and the test run for 1 hour. The water depth shall not exceed 
5 inches (127 mm) at any time during the 
measurement period. The drop that occurs during the final measurement period shall be used in calculating 
the percolation rate.
1114.2.2.2 Permeability tests.
Soil shall be evaluated for estimated percolation based 
on a permeability test 
performed in place, in accordance with procedures established by the New York City Department of Environ-
mental Protection and accepted engineering practice.
1114.3 Design.
The design of on
-
site stormwater disposal systems shall compl
y with the provisions of Section 
1114.3.1.
‡‡‡
1114.3.1 Runoff rate.
The runoff rate shall be calculated using the rational method, Equation 11
-
1. The cal-
culation shall incorporate the total site area with a rainfall intensity value of 
I
= 5.95 inches per 
hour. The weighted 
runoff coefficient shall be calculated using Equation 11
-
2 and shall incorporate the different combinations of sur-
faces using the 
C
values listed below.
Q
= 
C
w
× 
I
× 
A
(Equation 11
-
1)
Where: 
Q
=
developed flow, cubic feet per second 
C
w
=
weighted runoff coefficient 
I
=
the rainfall intensity value, 5.95 in/hr 
A
=
the total site area, acres (ac) 
C
w
=(1/
A
)
∑
(
A
K
×
C
K
)            
(
Equation 11
-
2)
STORM DRAINAGE
Where: 
C
w
= 
weighted runoff coefficient 
A
= 
The total site area, acres (ac) 
A
K
= 
The area of each surface coverage type, acres (ac)
C
K
= 
The runoff coefficient associated with each surface coverage type 
The following 
C
-
values shall be used for calculating a s
ite’s weighted runoff coefficient:
0.95
= 
roof/concrete
0.85
= 
asphalt
0.7 
= 
porous asphalt/concrete or permeable pavers
0.7 
= 
green roof with four or more inches of growing media
0.65
= 
gravel parking lot
0.3 
= 
undeveloped areas
0.2 
= 
gr
ass areas
0.2 
= 
rain gardens, vegetated swales and other surface green infrastructure practices
1114.3.1.1 Storage volume.
The storage volume of an on
-
site stormwater disposal system shall be measured 3 
feet (610 mm) above the level of the water table. The location of the water table shall be verified at the time of 
the field investigation conducted in accordance with Section
1114.2. Unless otherwise approved by the New 
York City Department of Environmental Protection, the storage volume of the on
-
site stormwater disposal sys-
tem shall accommodate the total stormwater volume calculated in this section. The stormwater volume sha
ll be 
calculated as follows:
1.
Compute the runoff rate using Equations 11
-
1 and 11
-
2.
2.
Calculate the outflow rate due to infiltration, in cubic feet per second, using Equation 11
-
3.
3.
Calculate the outflow rate, in cubic feet per second per acre, of im
perviousness using Equation 11
-
4.
4.
Calculate the duration of the design storm in minutes using Equation 11
-
5.
5.
Calculate the maximum required retention volume using Equation 11
-
6.
Q
inf
= (
FA
min
× 
i
soil
)/43,200
(Equation 11
-
3)
where:
Q
inf
=
outflow rate due to infiltration in cubic feet per second
FA
min
=
minimum footprint or surface area of the stormwater disposal system
i
soil
=
soil infiltration rate in inches per hour
Q
o
= 
C
WT
× 
i
× 
A
T
(Equation 11
-
4)
where:
Q
o
=
the 
average outflow rate in cubic feet per second during the rainfall event
C
WT
=
the weighted runoff coefficient for the tributary area
i
=
the average rainfall intensity in inches per hour for the event
A
T
=
the area tributary to the detention facility in a
cres
t
v
= 0.27 × (C
WT
× A
t
/Q
DRR
)
0.5
–
15
(Equation 11
-
5)
where:
t
v
=
the duration of the storm in minutes, with a 10 year
return frequency, requiring the maximum deten-
tion volume with a variable outflow
STORM DRAINAGE
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
Q
DRR
=
the detention f
acility maximum release rate in cubic feet per second
V
v
= (0.19 × C
WT
× At/(t
v
+ 15) 
–
40 × Q
DRR
) × t
v
(
Equation 11
-
6)
where:
V
V
=
the maximum required detention volume in cubic feet with a variable outflow 
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
t
v
=
the duration of the storm in minutes, with a 10 year return frequency, requiring the maximum deten-
tion volume with a variable outflow
Q
DRR
=
the detention facility maximum release rate in cubic feet per second
1114.4 Required components.
On
-
site stormwater
disposal systems shall be designed to provide adequate storage, 
support the use at the surface, and allow for operation and required maintenance. Systems shall be constructed with 
all necessary components and materials required by the manufacturers specif
ications. Drywell design shall incorporate 
a grit chamber, and where required, a sand column constructed in accordance with Figures 1114.4(1) and 1114.4(2), 
respectively.
STORM DRAINAGE
Figure 1114.4(1)
Grit Chamber
‡‡‡ Chapter 11 was amended by 
Local Law 
77 
of 2023
. This law has an effective
date of June 10, 2023.
CHAPTER 11
STORM DRAINAGE
SECTION PC 1101
GENERAL
1101.1 Scope. 
The provisions of this chapter shall govern the materials, design, construction and installation of storm 
drainage. Storm water discharge shall be in accordance with Department of Environmental Protection requirements. 
Extension requirements from the public storm or combined sewer to the building sewer shall be determined by the 
Department of Environmental Protection
. 
1101.2
Where required.
All roofs,
paved areas, yards
, courts and courtyards shall drain into a separate storm sewer 
system, or a combined sewer system, or to a place of disposal approved by the commissioner and in accordance with 
the requirements of the Department of Environmental Protection. An approved sy
stem for beneficial collection and 
use of storm water may be installed, in which case overflow from such a system shall be discharged to a safe location 
subject to the approval of the commissioner and the Department of Environmental Protection. See Section
107.6.2 
of this code for required construction documents relating to provisions for discharge for stormwater runoff.
1101.2.1 Increases in existing impervious surfaces.
Whenever impervious surfaces on the lot are increased, such 
impervious surfaces shall drain into a storm sewer system, or a combined sewer system, or 
to an approved place 
of disposal.
Exception:
An existing one
- 
or two
-
family dwelling where the area of a p
roposed horizontal building enlarge-
ment plus any proposed increase in impervious surfaces in total is less than or equal to 200 square feet (19 m
2
). 
In such cases, the storm water discharge may be accommodated by existing facilities. For the purposes of th
is 
exception, the 200 square feet (19 m
2
) shall include all enlargements and increases cumulatively after July 1, 
2008.
1101.2.2 Availability of public storm or combined sewer.
The determination as to whether a public storm sewer 
or public combined sewer i
s available to a building shall be made in accordance with applicable requirements of 
the Department of Environmental Protection.
1101.2.3 Feasibility of connecting to an available public storm or combined sewer.
The determination as to 
whether connection 
to an available public storm sewer or combined public sewer is feasible shall be made in ac-
cordance with applicable requirements of the Department of Environmental Protection.
1101.2.4 Extensions of public storm or combined sewers.
Extensions of public storm or combined sewers shall 
be made in accordance with the rules of the Department of Environmental Protection.
1101.3 Prohibited drainage.
Storm water shall not be drained into sewers intended for sewage only.
1101.4 Tests.
The conductors and the building
storm drain
shall be tested in accordance with Section 312.
1101.5 Change in size.
The size of a drainage pipe shall not be reduced in the direction of flow.
Exception:
Drainage pipe that is part of an approved detention or retention system.
1101.
5.1 
Detention systems.
Where a detention system is provided, the pipe leaving the detention tank shall be per-
mitted to be reduced to the flow allowed by the Department of Environmental Protection, provided, however, that an 
emergency overflow shall be provided
to protect the building from internal flooding. 
1101.
5.2 Detention and retention tanks. 
Detention and retention tanks located within buildings in flood hazard areas 
shall be located above the design flood elevation or shall be designed and constructed to
withstand the static pressure 
conditions the system will experience in the event of a flood condition.
1101.5.2.1 Emergency overflow.
Emergency overflow piping shall equal the full size of the incoming storm 
water flow. Emergency overflows and vent terminations for buildings located in flood hazard areas shall be 
STORM DRAINAGE
located above the design flood elevation. Such emergency overflow shall discharge the overflow outside of the 
building into either of the following locations:
1.
The tax lot; or
2.
The public sewe
r, provided that the overflow piping is provided with a vent, of the same diameter as the 
overflow piping, that terminates on the front wall of the building facing the street and no more than 2 feet 
(610 mm) above the sidewalk See Figures 1101.5.2.1(1), 11
01.5.2.1(2) and 1101.5.2.1(3).
Detention Volume & Tank Above Grade (Within Building)
Figure 1101.5.2.1(1)
‡
STORM DRAINAGE
Detention Volume Above Sewer, Tank Below Grade (Within Building)
Figure 1101.5.2.1(2)
‡
Detention Volume & Tank Below Grade (Within 
Building)
Figure 1101.5.2.1(3)
‡
STORM DRAINAGE
1101.6 Fittings and connections.
All connections and changes in direction of the storm drainage system shall be 
made with approved drainage
-
type fittings in accordance with Table 706.3. The fittings shall not obstruct or re
tard 
flow in the system.
1101.7 Roof design. 
Roofs shall be designed for the maximum possible depth of water that will pond thereon as 
determined by the relative levels of roof deck and overflow weirs, scuppers, edges or serviceable drains in combination 
w
ith the deflected structural elements. In determining the maximum possible depth of water, all primary roof 
drainage 
means shall be assumed to be blocked
. The maximum possible depth of water on the roof shall include the height of 
the water required above 
the inlet of the secondary roof drainage means to achieve the required flow rate of the sec-
ondary drainage means to accommodate the design rainfall rate as required by Section 1106.
1101.8 Cleanouts required.
Cleanouts shall be installed in the storm drain
age system and shall comply with the 
provisions of this code for sanitary drainage pipe cleanouts.
Exception: 
Subsurface drainage system.
1101.9 Backwater valves. 
Storm drainage systems shall be provided with backwater valves as required for 
sanitary 
drainage systems in accordance with Section 715.
1101.9.1 Backwater valves in flood hazard areas.
Backwater valves for all buildings located in flood hazard 
areas shall be installed in storm drainage systems in accordance with the requirements of 
this code and the addi-
tional requirements of Section 7.3.4 of ASCE 24 as modified by Appendix G of the 
New York City Building Code
.
1101.10 Plastic pipe.
Plastic piping and fittings shall not be used.
Exceptions:
1.
Plastic piping and fittings may be used 
in residential buildings five stories or less in height.
2.
Corrugated polyethylene and corrugated polypropylene piping and fittings, with a diameter of 12 inches (305 
mm) or more may be used in connection with any type of building for under
-
ground yard dr
ainage and storm 
water piping when used outside of the foundation wall of the building and not connecting to any piping 
system from the interior of the building. 
1101.11 Cured
-
in
-
place pipe.
Cured
-
in
-
place pipe (CIPP) and epoxy spray pipe lining systems s
hall not be used.
1101.12 Site grading.
Except as otherwise permitted by this code, no person shall perform site grading or land 
contour work, as defined in Section 19
-
137 of the 
Administrative Code
, that would cause storm water to flow across 
sidewalks or
onto an adjacent property. Site grading or land contour work performed on the site of a covered devel-
opment project shall comply with the rules of the Department of Environmental Protection and this code.
SECTION 
PC 
1102
MATERIALS
1102.1 General. 
The materials and methods utilized for the construction and installation of storm drainage systems 
shall comply with this section and the applicable provisions of Chapter 7.
1102.2 Storm drainage conductors and leaders. 
Storm drainage condu
ctors and leaders shall conform to Sections 
1102.2.1 and 1102.2.2.
1102.2.1 Inside storm drainage conductors. 
Inside storm drainage conductors installed above ground shall con-
form to one of the standards listed in Table 702.1.
1102.2.2 Exterior storm drain
age leaders. 
Exterior storm
drainage leaders installed above ground shall conform 
to one of the standards listed in Table 702.1.
Exception: 
Exterior storm drainage leaders installed above ground for buildings in occupancy group R
-
3 and 
bulkheads draining t
o other roof surfaces.
1102.3 Underground building storm drain pipe. 
Underground building storm drain
pipe shall conform to one of 
the standards listed in Table 702.2.
STORM DRAINAGE
1102.4 Building storm sewer pipe. 
Building storm sewer
pipe shall conform to one of the 
standards listed in Table 
1102.4. 
TABLE 1102.4
BUILDING STORM SEWER PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Chlorinated polyvinyl chloride 
(CPVC) plastic
b
ASTM F 437; ASTM F 438; 
ASTM F 439
Concrete pipe
ASTM C 14; 
ASTM C 76;
CSA A257.1M; CSA 
A257.2M
Copper or copper
-
alloy tubing 
(Type K or L)
ASTM B 75; ASTM B 88; 
ASTM B 251
Ductile
-
iron pipe
AWWA C151
Galvanized steel pipe
ASTM A 53; ASTM A 123
High density polyethylene pipe 
(HDPE)
a
ASTM D 3350
Polyvinyl chloride (PVC) plas-
tic pipe (Type DWV, SDR26, 
SDR35, SDR41, PS50 or 
PS100)
b
ASTM D 2665; ASTM D 
3034; ASTM F 891; CSA 
B182.4; CSA B181.2; CSA 
B182.2
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; 
ASTM C 700
a. Approved plastic sewer for piping 12 inches and larger in accordance with Section 1101.10, Exception 2.
b.
Limited to residential buildings five stories or less in height.
1102.5 Subsoil drain pipe. 
Subsoil drains shall be 
open jointed
, horizontally split or perforated pipe conforming to 
one of the standards listed in Table 1102.5.
TABLE 1102.5
SUBSOIL DRAIN PIPE
MATERIAL
STANDARD
Cast
-
iron pipe
ASTM A 74; ASTM A 888; 
CISPI 301
Polyethylene (PE) plastic pipe
ASTM F 405; CSA B182.1; 
CSA B182.6; CSA B182.8
Polypropylene (PP) plastic 
pipe
ASTM F 2764; ASTM F 3219
STORM DRAINAGE
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe, 
SDR35, PS25, PS50 or 
PS100)
a
ASTM D 2729; ASTM D 
3034; ASTM F 
891; CSA 
B182.2; CSA B182.4
Porous concrete pipe
ASTM C 654
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay pipe
ASTM C 4; ASTM C 700
a.
Limited to residential buildings five stories or less in height.
1102.6 Roof drains. 
Roof drains shall conform to ASME A112.6.4
or ASME A112.3.1.
1102.7 Fittings. 
Pipe fittings shall be approved for installation with the piping material installed, and
shall conform 
to the respective pipe standards or one of the standards listed in Table 1102.7. The fittings shall not have ledges, 
shoulders or reductions capable of retarding or obstructing flow in the piping. Threaded drainage pipe fittings shall be 
of 
the recessed drainage type.
TABLE 1102.7
PIPE FITTINGS
MATERIAL
STANDARD
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in IPS di-
ameters
a
ASTM D 2661; ASTM F 628; 
CSA B181.1
Acrylonitrile butadiene styrene 
(ABS) plastic pipe in sewer 
and 
drain diameters
ASTM D 2751
Brass
ASTM B 62
Cast
-
iron
ASME B16.4; ASME B16.12; 
ASTM A 888; CISPI 301; 
ASTM A 74
Chlorinated polyvinyl chloride 
(CPVC) plastic
a
ASTM 
F 437
; ASTM 
F 438
; 
ASTM F 
439
Copper or copper
-
alloy tubing 
(Type K, L)
ASTM B 75; 
ASTM B 88; 
ASTM B 251
Ductile iron
AWWA C110
Galvanized steel
ASTM A 153; ASME B16.3
High
-
density polyethylene 
(HDPE)
ASTM D 3350
Malleable iron
ASME B16.3
STORM DRAINAGE
Polyethylene (PE) plastic pipe
a
ASTM F 2306/F 2306M
Polyolefin
a
CSA B 181.3; 
ASTM F 
1412; 
ASTM D 2657
Polypropylene (PP) plastic 
pipe
a
ASTM F 2764; ASTM F 3219
Polyvinyl chloride (PVC)
plastic
a
ASTM D 2464; ASTM D 
2466; ASTM D 2467; CSA 
B137.2; ASTM D 2665; 
ASTM D 3311; ASTM F 1866
Polyvinyl chloride (PVC) 
plastic pipe in sewer and drain 
diameters
a
ASTM D 3034
Polyvinylidene fluoride 
(PVDF) plastic pipe
a
ASTM F 1673; CSA B181.3
Stainless steel drainage sys-
tems, Type 316L
ASME A112.3.1
Vitrified clay
ASTM C 425
a.
Limited to 
residential buildings five stories or less in height.
SECTION PC 1103
TRAPS
1103.1 Main trap. 
Leaders and storm drains connected to a combined sewer shall be trapped. Individual storm water 
traps shall be installed on the storm water drain branch serving each conductor, or a single trap shall be installed in 
the main storm drain just before its con
nection with the combined building sewer or the public sewer. 
A hooded catch 
basin located within the property line shall be the equivalent of a building
-
house trap for the connection to a public 
sewer.
1103.2 Material. 
Storm water traps shall be of an app
roved material in accordance with Table 1102.7.
1103.3 Size. 
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
1103.4 Cleanout. 
An accessible cleanout shall be installed on the building side of the 
trap.
SECTION PC 1104
CONDUCTORS AND CONNECTIONS
1104.1 Prohibited use. 
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes 
shall not be used as conductors.
1104.2 Floor drains. 
Floor drains shall not be connected 
to a storm drain.
1104.3 Combining storm with sanitary drainage.
The sanitary and storm drainage systems of a structure shall be 
entirely separate except for minor modifications to existing buildings having combined systems. Where a combined 
building drain
is utilized, the building storm drain shall be connected in the same horizontal plane through a single
-
wye fitting to the building drain at least 10 feet (3048 mm) downstream from any soil stack. If a separate city storm 
sewer is not available, building s
anitary drains shall be separate and shall only be permitted to connect to a common 
building combined drain downstream of building (house) trap.
1104.4 Clear water drains.
Drains carrying clear water, i.e., air
-
conditioning drips, pump drips, cooling water
, etc., 
may discharge into the storm water drainage system through an indirect waste connection discharging into a trapped 
funnel or raised lip floor drain.
STORM DRAINAGE
Exception:
Cooling tower blow
-
down shall discharge into the sanitary drainage system.
1104.5 Parkin
g garage floor drains.
Floor drains provided in open or enclosed parking garages shall drain to the 
storm drainage system.
Exception:
Where the storm drainage system discharges to a dedicated storm sewer, parking garage floor drains 
shall be connected to t
he sanitary drainage system.
SECTION PC 1105
ROOF DRAINS
1105.1 
General.
Roof drains shall be installed in accordance with the manufacturer’s instructions. The inside opening 
for the roof drain shall not be obstructed by the roofing membrane material.
1105
.2
Roof drain flow rate. 
The published roof drain flow rate, based on the head of water above the roof drain, 
shall be used to size the storm drainage system in accordance with Section 1106. The flow rate used for sizing the 
storm drainage piping shall be 
based on the maximum anticipated ponding at the roof drain.
SECTION PC 1106
SIZE OF CONDUCTORS, LEADERS AND STORM DRAINS
‡‡‡
1106.1 General. 
The size of the vertical conductors and 
leaders, gutters,
building storm drains, building storm 
sewers and any horizontal branches of such drains or sewers
shall be based on the 100
-
year hourly rainfall rate 
of 3 
inches (76 mm) per hour. Sizing for secondary and combined primary and secondary conductors, leaders
and drains 
shall be in accordance with Section 1108
.
1106.2 Size of storm drain piping. 
Vertical and horizontal storm drain piping shall be sized based on the flow rate 
through the roof drain. The flow rate in storm drain piping shall not exceed that 
specified in Table 1106.2.
TABLE 1106.2
STORM DRAIN PIPE SIZING
PIPE SIZE (inches)
CAPACITY (gpm)
VERTICAL DRAIN
SLOPE OF HORIZONTAL DRAIN
1
/
16
inch per foot
1
/
8
inch per foot
1
/
4
inch per foot
1
/
2
inch per foot
2
34
15
22
31
44
3
87
39
55
79
111
4
180
81
115
163
231
5
311
117
165
234
331
6
538
243
344
487
689
8
1,117
505
714
1,010
1,429
10
2,050
927
1,311
1,855
2,623
12
3,272
1,480
2,093
2,960
4,187
14
4,204
1,312
1,856
2,621
3,713
15
5,543
2,508
3,546
5,016
7,093
STORM DRAINAGE
16
5,543
2,508
3,546
5,016
7,093
18
8.218
3,100
4,386
6,192
8,773
1106.2.1 Values for continuous flow. 
Where there is a continuous or semicontinuous discharge into the building 
storm drain or building storm sewer, such as from a pump, ejector, air conditioning plant or 
similar device, each 
gallon per minute of such discharge shall be computed as being equivalent to 32 square feet (2.97 m
2
) of roof area, 
based on a rainfall rate of 3 inches (75 mm) per hour.
1106.3 Vertical leader sizing. 
Vertical leaders shall be sized b
ased on the flow rate from horizontal gutters or the 
maximum flow rate through roof drains. The flow rate through vertical leaders shall not exceed that specified in Table 
1106.3.
STORM DRAINAGE
TABLE 1106.3
VERTICAL LEADER SIZING
SIZE OF LEADER
(inches)
CAPACITY
(gpm)
2
30
2 × 2
30
1
1
/
2
× 2
1
/
2
30
2
1
/
2
54
2
1
/
2
× 2
1
/
2
54
3
92
2 × 4
92
2
1
/
2
× 3
92
4
192
3 × 4
1
/
4
192
3
1
/
2
× 4
192
5
360
4 × 5
360
4
1
/
2
× 4
1
/
2
360
6
563
5 × 6
563
5
1
/
2
× 5
1
/
2
563
8
1208
6 × 8
1208
For SI: 1 inch = 25.4 mm, 1 gallon per 
minute = 3.785 L/m.
1106.4 Vertical walls. 
In sizing roof drains and storm drainage piping, one
-
fourth of the area of any vertical wall that 
diverts rainwater to the roof or the setback roof of a building shall be added to the projected roof area for inclu
sion in 
calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Exceptions:
1.
Where vertical conductors or leaders and downstream piping has been sized for secondary roof drainage in 
accordance with Section 1108
, the contribution from vertical walls need not be added to the projected roof 
area.
2.
Section 1106.4 shall not be applicable to vertical walls fronting a public right
-
of
-
way.
1106.5 Parapet wall scupper location. 
Parapet wall roof drainage scupper and overflow scupper location shall com-
ply with the requirements of Section 1503.4 of 
the 
New York City 
Building Code
.
STORM DRAINAGE
1106.6 Size of roof gutters.
Horizontal
gutters shall be sized based on the 
flow rate from the
roof surface. The flow 
rate in horizontal gutters shall not exceed that specified in Table 1106.6.
TABLE 1106.6
HORIZONTAL GUTTER SIZING
GUTTER DIMENSIONS
a
(inches)
SLOPE
(inch per foot)
CAPACITY
(gpm
)
1
1
/
2
× 2
1
/
2
1
/
4
26
1
1
/
2
× 2
1
/
2
1
/
2
40
4
1
/
8
39
2
1
/
4
× 3
1
/
4
55
2
1
/
4
× 3
1
/
2
87
5
1
/
8
74
4 × 2
1
/
2
1
/
4
106
3 × 3
1
/
2
1
/
2
156
6
1
/
8
110
3 × 5
1
/
4
157
3 × 5
1
/
2
225
8
1
/
16
172
8
1
/
8
247
4
1
/
2
× 6
1
/
4
348
4
1
/
2
× 6
1
/
2
494
10
1
/
16
331
10
1
/
8
472
5 × 8
1
/
4
651
4 × 10
1
/
2
1055
For SI:
1 inch = 25.4 mm, 1 foot = 304.8 mm, 
1 gallon per minute = 3.785 L/m, 1 inch per foot = 83.3 mm/m.
a.
Dimensions are width by depth for rectangular shapes. Single dimensions are diameters of a sem
icircle.
SECTION PC 1107
SIPHONIC ROOF DRAINAGE SYSTEMS 
STORM DRAINAGE
1107.1 General. 
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 
and ASPE 45.
SECTION PC 1108
SECONDARY (EMERGENCY) ROOF DRAINS
1108.1 Secondary (emergency overflow) drains or scuppers. 
Where roof drains are required, secondary (emergency 
overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in 
such a manner that water will
be entrapped if the primary drains allow buildup for any reason. 
The inlet elevation of 
secondary (overflow) drains and the invert elevation of overflow scuppers should be not less than 2 inches (51 mm) 
or more than 4 inches (102 mm) above the low point o
f the (adjacent to) roof surface unless a safer water depth 
loading, including the required hydraulic head to maintain required flow rate out of the overflow drainage system 
that has been determined by the structural design. 
Where primary and secondary roo
f drains are manufactured as a 
single assembly, the inlet and outlet for each drain shall be independent.
1108.2 Separate systems required. 
Secondary roof drain systems shall have the end point of discharge separate from 
the primary system. Discharge shall
be above grade, in a location 
that
would normally be observed by the building 
occupants or maintenance personnel
. 
Exception:
Secondary drainage system may tie into the primary drainage system in the vertical conductors 
where 
separate systems are impracti
cal or to prevent water from flowing over sidewalk or pedestrian walkways.
1108.3 Sizing of secondary drains. 
Secondary (emergency) roof drain systems shall be sized in accordance with 
Section 1106 based on the rainfall rate 
of 3 inches (76 mm) per hour
. S
cuppers shall be sized to prevent the depth of 
ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall 
have an opening dimension of not less than 4 inches (102 mm). 
The flow through the primary syst
em shall not be 
considered when sizing the secondary roof drain system.
Exception:
Where secondary drainage systems tie into primary drainage systems, the combined primary and sec-
ondary system shall be sized based on their combined rainfall rate of 6 inche
s (152 mm) per hour.
SECTION PC 1109
COMBINED SANITARY AND STORM 
SYSTEM
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new instal-
lations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable 
requirements of the Department of Environmental Protection. With respect to 
repair of combined systems installed 
prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be com-
puted in accordance with the method in Section 1106. The fixture units shall be converted into an equi
valent pro-
jected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, 
the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m
2
). Where the total 
fixture 
load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square 
feet (0.48 m
2
) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
SECTION PC 1110
CONTROLLED FLOW ROOF DRAIN 
SYSTEMS
1110.1 General. 
The roof of a structure shall be designed for the storage of water where the storm drainage system is 
engineered for controlled flow. The controlled flow roof drain 
system
shall be an engineered system in accordance 
with this sectio
n and Section 
28
-
113.2.2 of the 
Administrative Code
.
The controlled flow system shall be designed 
based on the 
design
rainfall rate in accordance with Section 1106.1.
1110.2 Control devices. 
The control devices shall be installed so that the rate of discha
rge of water per minute shall 
not exceed the values for controlled flow as 
allowed by the Department of Environmental Protection
.
1110.3 Installation. 
Runoff control shall be by control devices. Control devices shall be protected by strainers.
STORM DRAINAGE
1110.4 Minim
um number of roof drains. 
Not less than two roof drains shall be installed in roof areas 10,000 square 
feet (929 m
2
) or less and not less than four roof drains shall be installed in roofs over 10,000 square feet (929 m
2
) in 
area.
SECTION 
PC 
1111
SUBSOIL DR
AINS
1111.1 Subsoil drains. 
Subsoil drains 
carrying groundwater 
shall be open
-
jointed, horizontally split or perforated 
pipe conforming to one of the standards listed in Table 1102.5. Such drains shall not be less than 4 inches (102 mm) 
in diameter. Where 
the building is subject to backwater, the subsoil drain shall be protected by an accessibly located 
backwater valve. 
Subsoil drainage discharged into a public sewer shall be approved by the Department of Environ-
mental Protection. The subsoil
drains
shall discharge into a readily accessible silt and sand interceptor before being 
connected into the gravity drainage or sump system. Subsoil drainage 
shall discharge to a trapped area drain, sump, 
dry well or approved location above ground. The subsoil su
mp shall not be required to have either a gas
-
tight cover 
or a vent. The sump and pumping system shall comply with Section 1113.1.
SECTION 
PC 
1112
BUILDING SUBDRAINS
1112.1 Building subdrains. 
Building subdrains located below the public sewer level shall d
ischarge into a sump or 
receiving tank, the contents of which shall be automatically lifted and discharged into the drainage system as required 
for building sumps. The sump and pumping equipment shall comply with Section 1113.1.
SECTION 
PC 
1113
SUMPS AND P
UMPING SYSTEMS
1113.1 Pumping system. 
The sump pump, pit and discharge piping shall conform to Sections 1113.1.1 through 
1113.1.4.
1113.1.1 Pump capacity and head. 
The sump pump shall be of a capacity and head appropriate to anticipated use 
requirements.
1
113.1.2 Sump pit. 
The sump pit shall be not less than 18 inches (457 mm) in diameter and not less than 24 inches 
(610 mm) 
in depth
, unless otherwise approved. The pit shall be accessible and located such that all drainage flows 
into the pit by gravity. The
sump pit shall be constructed of tile, steel, plastic, cast iron, concrete or other approved 
material, with a removable cover adequate to support anticipated loads in the area of use. The pit floor shall be 
solid and provide permanent support for the pump
.
1113.1.3 Electrical. 
Electrical service outlets, when required, shall meet the requirements of 
the 
New York City 
Electrical Code
.
1113.1.4 Piping. 
Discharge piping shall meet the requirements of Section 1102.2, 1102.3 or 1102.4 and shall in-
clude a gate v
alve and a full flow check valve. Pipe and fittings shall be the same size as, or larger than, the pump 
discharge 
tapping.
Exception: 
In one
-
and two
-
family dwellings, only a check valve shall be required, located on the discharge 
piping from the pump or e
jector.
SECTION PC 1114
PRIVATE ON
-
SITE STORMWATER DISPOSAL SYSTEMS
1114.1 General.
Private on
-
site stormwater disposal systems shall comply with the provisions of Section 1114.
1114.1.1 When permitted.
The use of private on
-
site stormwater disposal system
s shall be permitted only in the 
following circumstances:
STORM DRAINAGE
1.
Pursuant to a certification issued by the New York City Department of Environmental Protection that a public 
storm or combined sewer is not available or that connection thereto is not feasible in accordance with Section 
107.6.2.2, Item 1(i);
2.
Pursuant to
a certification submitted by the applicant to the New York City Department of Environmental 
Protection that a public storm or combined sewer is not available or that connection thereto is not feasible, 
in such cases where the availability and feasibility 
of connection to a public storm or combined sewer are 
allowed to be certified by the applicant pursuant to rules of the New York City Department of Environmental 
Protection, in accordance with Section 107.6.2.2, Item 1(ii);
3.
Pursuant to a certification s
ubmitted by the applicant to the New York City Department of Environmental 
Protection authorizing on
-
site stormwater disposal in accordance with Section 107.6.2.1, Item 1;
4.
For enlargements less than 1000 square feet (93 m
2
) in accordance with Section 107.6.2, Exception 2;
5.
For outdoor drinking fountains; or
6.
The disposal of foundation drainage as described in Section 1807.4.3 of the 
New York City Building Code
.
1114.1.2 Acceptable systems.
Acceptable on
-
site stormwater 
disposal systems shall include:
1.
Drywells;
2.
Gravel beds;
3.
Perforated pipe;
4.
Stormwater chambers that facilitate infiltration; and
5.
Alternate method of on
-
site disposal as approved by the department and the New York City Department of 
Environmenta
l Protection.
1114.1.3 Minimum setbacks.
On
-
site stormwater disposal systems shall be located at least 5 feet (1524 mm) from 
all lot lines except where the lot line abuts a public right of way and 10 feet (3048 mm) from all foundations or 
walls existing on
the date of application for a building permit or proposed under the application to construct the 
on
-
site stormwater disposal system. Systems shall be located 20 feet (6096 mm) from disposal fields and 20 feet 
(6096 mm) from seepage pits. On
-
site stormwate
r disposal systems shall not be located within the building foot-
print.
1114.2 Field investigation.
The size of an on
-
site stormwater disposal system shall be predicated on a field investi-
gation performed prior to construction document approval that is perf
ormed at the site of a proposed on
-
site storm-
water disposal system to assess the suitability of the soil and site. The investigation shall conform to Sections 1114.2.1 
and 1114.2.2 and shall occur prior to approval of construction documents for the system.
The field investigation shall 
be subject to special inspection in accordance with Section 1704.21 of the 
New York City Building Code
.
‡‡‡
1114.2.1 Classification of soil based on borings and test pits.
At least one boring and one test pit shall be 
made at
the approximate site of each proposed on
-
site stormwater disposal system. Soil borings and sampling 
procedures shall in accordance with ASTM D 1586 and ASTM D 1587, and generally accepted engineering prac-
tice. Soil and rock samples shall be classified in 
accordance with Section 1802.3 of the 
New York City Building 
Code
.
1114.2.2 Soil infiltration capabilities.
The suitability of the subsurface soils must be verified in place by either a 
percolation test or a permeability test. Where testing determines that
the infiltration rate of the subsurface soils is 
less than 
1
/
2
inch (12.7 mm) per hour, private on
-
site stormwater disposal systems shall not be permitted. Such tests 
shall conform to Section 1114.2.2.1 or 1114.2.2.2, as applicable.
1114.2.2.1 Percolation
tests and procedures.
The infiltration rate of subsurface soils shall be verified with a 
percolation test. Percolation tests shall be performed in accordance with Sections 1114.2.2.1.1 through 
1114.2.2.1.3 under the supervision of a special inspection age
ncy in accordance with Section 1704.21.1 of the 
New York City Building Code
. At least one percolation test in each system area shall be conducted. The holes 
shall be spaced uniformly in relation to the bottom depth of the proposed absorption system. More p
ercolation 
STORM DRAINAGE
tests shall be made where necessary, depending on system design. The results of the percolation tests shall be 
filed with the department stating the suitability of the site and the capacity of the subsoil for the proposed use.
1114.2.2.1.1 Perco
lation test hole.
The test hole shall be dug or bored. The test hole shall have vertical sides 
and a horizontal dimension of 4 inches to 8 inches (102 mm to 203 mm). The bottom and sides of the hole 
shall be scratched with a sharp
-
pointed instrument to exp
ose the natural soil. All loose material shall be 
removed from the hole and the bottom shall be covered with 2 inches (51 mm) of gravel or coarse sand.
1114.
2.2.1.2 Test procedure, sandy soils.
The hole shall be filled with clear water to a minimum of 12 
inches (305 mm) above the bottom of the hole for tests in sandy soils. The time for this amount of water to 
seep away shall be determined, and this procedure shall be repeated if the water from 
the second filling of 
the hole seeps away in 10 minutes or less. The test shall proceed as follows: Water shall be added to a point 
not more than 6 inches (152 mm) above the gravel or coarse sand. Thereupon, from a fixed reference point, 
water levels shall
be measured at 10
-
minute intervals for a period of 1 hour. Where 6 inches (152 mm) of 
water seeps away in less than 10 minutes, a shorter interval between measurements shall be used, but in no 
case shall the water depth exceed 6 inches (152 mm). Where 6 i
nches (152 mm) of water seeps away in less 
than 2 minutes, the test shall be stopped and a rate of less than 3 minutes per inch (7.2 s/mm) shall be reported. 
The final water level drop shall be used to calculate the percolation rate. Soils not meeting the 
above require-
ments shall be tested in accordance with Section 1114.2.2.1.3.
1114.
2.2.1.3 Test procedure, other soils.
The hole shall be filled with clear water, and a minimum water 
depth of 12 inches (305 mm) shall be maintained above the bottom of the hol
d for a 4
-
hour period by refilling 
whenever necessary or by use of an automatic siphon. Water remaining in the hole after 4 hours shall not be 
removed. Thereafter, the soil shall be allowed to swell not less than 16 hours or more than 30 hours. Imme-
diately
after the soil swelling period, the measurements for determining the percolation rate shall be made as 
follows: Any soil sloughed into the hole shall be removed and the water level shall be adjusted to 6 inches 
(152 mm) above the gravel or coarse sand. Th
ereupon, from a fixed reference point, the water level shall be 
measured at 30
-
minute intervals for a period of 4 hours, unless two successive water level drops do not vary 
by more than 
1
/
16
inch (1.59 mm). At least three water level drops shall be observe
d and recorded. The hole 
shall be filled with clear water to a point not more than 6 inches (152 mm) above the gravel or coarse sand 
whenever it becomes nearly empty. Adjustments of the water level shall not be made during the three meas-
urement periods exc
ept to the limits of the last measured water level drop. When the first 6 inches (152 mm) 
of water seeps away in less than 30 minutes, the time interval between measurements shall be 10 minutes 
and the test run for 1 hour. The water depth shall not exceed 
5 inches (127 mm) at any time during the 
measurement period. The drop that occurs during the final measurement period shall be used in calculating 
the percolation rate.
1114.2.2.2 Permeability tests.
Soil shall be evaluated for estimated percolation based 
on a permeability test 
performed in place, in accordance with procedures established by the New York City Department of Environ-
mental Protection and accepted engineering practice.
1114.3 Design.
The design of on
-
site stormwater disposal systems shall compl
y with the provisions of Section 
1114.3.1.
‡‡‡
1114.3.1 Runoff rate.
The runoff rate shall be calculated using the rational method, Equation 11
-
1. The cal-
culation shall incorporate the total site area with a rainfall intensity value of 
I
= 5.95 inches per 
hour. The weighted 
runoff coefficient shall be calculated using Equation 11
-
2 and shall incorporate the different combinations of sur-
faces using the 
C
values listed below.
Q
= 
C
w
× 
I
× 
A
(Equation 11
-
1)
Where: 
Q
=
developed flow, cubic feet per second 
C
w
=
weighted runoff coefficient 
I
=
the rainfall intensity value, 5.95 in/hr 
A
=
the total site area, acres (ac) 
C
w
=(1/
A
)
∑
(
A
K
×
C
K
)            
(
Equation 11
-
2)
STORM DRAINAGE
Where: 
C
w
= 
weighted runoff coefficient 
A
= 
The total site area, acres (ac) 
A
K
= 
The area of each surface coverage type, acres (ac)
C
K
= 
The runoff coefficient associated with each surface coverage type 
The following 
C
-
values shall be used for calculating a s
ite’s weighted runoff coefficient:
0.95
= 
roof/concrete
0.85
= 
asphalt
0.7 
= 
porous asphalt/concrete or permeable pavers
0.7 
= 
green roof with four or more inches of growing media
0.65
= 
gravel parking lot
0.3 
= 
undeveloped areas
0.2 
= 
gr
ass areas
0.2 
= 
rain gardens, vegetated swales and other surface green infrastructure practices
1114.3.1.1 Storage volume.
The storage volume of an on
-
site stormwater disposal system shall be measured 3 
feet (610 mm) above the level of the water table. The location of the water table shall be verified at the time of 
the field investigation conducted in accordance with Section
1114.2. Unless otherwise approved by the New 
York City Department of Environmental Protection, the storage volume of the on
-
site stormwater disposal sys-
tem shall accommodate the total stormwater volume calculated in this section. The stormwater volume sha
ll be 
calculated as follows:
1.
Compute the runoff rate using Equations 11
-
1 and 11
-
2.
2.
Calculate the outflow rate due to infiltration, in cubic feet per second, using Equation 11
-
3.
3.
Calculate the outflow rate, in cubic feet per second per acre, of im
perviousness using Equation 11
-
4.
4.
Calculate the duration of the design storm in minutes using Equation 11
-
5.
5.
Calculate the maximum required retention volume using Equation 11
-
6.
Q
inf
= (
FA
min
× 
i
soil
)/43,200
(Equation 11
-
3)
where:
Q
inf
=
outflow rate due to infiltration in cubic feet per second
FA
min
=
minimum footprint or surface area of the stormwater disposal system
i
soil
=
soil infiltration rate in inches per hour
Q
o
= 
C
WT
× 
i
× 
A
T
(Equation 11
-
4)
where:
Q
o
=
the 
average outflow rate in cubic feet per second during the rainfall event
C
WT
=
the weighted runoff coefficient for the tributary area
i
=
the average rainfall intensity in inches per hour for the event
A
T
=
the area tributary to the detention facility in a
cres
t
v
= 0.27 × (C
WT
× A
t
/Q
DRR
)
0.5
–
15
(Equation 11
-
5)
where:
t
v
=
the duration of the storm in minutes, with a 10 year
return frequency, requiring the maximum deten-
tion volume with a variable outflow
STORM DRAINAGE
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
Q
DRR
=
the detention f
acility maximum release rate in cubic feet per second
V
v
= (0.19 × C
WT
× At/(t
v
+ 15) 
–
40 × Q
DRR
) × t
v
(
Equation 11
-
6)
where:
V
V
=
the maximum required detention volume in cubic feet with a variable outflow 
C
WT
=
the weighted runoff coefficient for the area tributary to the detention facility
A
T
=
the area tributary to the detention facility in square feet
t
v
=
the duration of the storm in minutes, with a 10 year return frequency, requiring the maximum deten-
tion volume with a variable outflow
Q
DRR
=
the detention facility maximum release rate in cubic feet per second
1114.4 Required components.
On
-
site stormwater
disposal systems shall be designed to provide adequate storage, 
support the use at the surface, and allow for operation and required maintenance. Systems shall be constructed with 
all necessary components and materials required by the manufacturers specif
ications. Drywell design shall incorporate 
a grit chamber, and where required, a sand column constructed in accordance with Figures 1114.4(1) and 1114.4(2), 
respectively.
STORM DRAINAGE
Figure 1114.4(1)
Grit Chamber
STORM DRAINAGE
FIGURE 1114.4(2)
DETAIL OF DRYWELL WITH SAND 
COLUMN
1114.4.1 Grit chamber.
All drywells shall contain a grit chamber as part of the drywell system. Grit chambers 
shall be constructed in accordance with the following requirements:
1.
Solid access cover with a minimum diameter of 15 inches (381 
mm).
2.
Grit chamber designed to support the maximum anticipated load.
3.
Outlet invert elevation shall be a minimum of 1 inch (25 mm) lower than the lowest inlet elevation.
4.
The sump shall be a minimum of 18 inches (450 mm) or two times the largest inle
t pipe diameter, whichever 
is greater, as measured to the outlet invert elevation.
5.
The interior dimensions shall be a minimum of 18 inches (450 mm) or four times the largest inlet pipe diam-
eter whichever is greater.
1114.4.2 Reserved.
1114.5 On
-
site sto
rmwater disposal system installation.
On
-
site stormwater disposal systems shall be installed in 
accordance the manufacturer’s recommendations and shall conform to Sections 1114.5.1 through 1114.5.3.
1114.5.1 Support of excavation.
When an on
-
site stormwate
r disposal system installation requires an excavation 
deeper than 5 feet (1524 mm), the sides of the excavation shall be protected and maintained in accordance with 
Section 3304.4 of the 
New York City Building Code
.
STORM DRAINAGE
1114.5.2 Sand column installation.
Where
the installation of an on
-
site stormwater disposal system requires the 
installation of a sand column, measures shall be taken to ensure the sand column is installed without contamination 
by impervious materials.
1114.5.3 Verification.
The department reser
ves the right to require a 24
-
hour test to verify the absorption of water 
in the installed on
-
site stormwater disposal system prior to final approval.
1114.6 Special inspection.
The installation of on
-
site stormwater disposal systems shall be subject to sp
ecial inspec-
tion in accordance with Section 1704.21 of the 
New York City Building Code
. Minor variations, based on actual site 
conditions, shall be acceptable at the discretion of the registered design professional of record. 
1114.7 Maintenance.
The prope
rty owner shall maintain any on
-
site stormwater disposal system in proper working 
order in accordance with the rules of the Department of Environmental Protection.
1114.8 Signage.
Signage shall be attached to the house trap or fresh air pipe in the basemen
t that states: AN ON
-
SITE 
STORMWATER DISPOSAL SYSTEM IS LOCATED ON THIS PROPERTY FOR STORMWATER DISPOSAL. 
INSPECTION AND MAINTENANCE OF THIS ON
-
SITE STORMWATER DISPOSAL SYSTEM IS REQUIRED 
BY THE RULES OF THE DEPARTMENT OF ENVIRONMENTAL PROTECTION. This sig
nage shall depict the 
location of the system on the property.
1114.9 Post
-
construction stormwater management facilities required by stormwater pollution prevention plan.
A post
-
construction stormwater management facility that is constructed as part of a co
vered development project shall 
be designed, installed and maintained in accordance with the rules of the Department of Environmental Protection and 
this code.