ADOPTS WITH AMENDMENTS:

International Plumbing Code 2015 (IPC 2015)

Heads up: There are no amended sections in this chapter.
The provisions of this chapter shall govern the materials, design, construction and installation of storm drainage.

1101.2 Disposal

AMENDMENT
This section has been amended at the state or city level.
Rainwater from roofs and storm water from paved areas, yards, courts and courtyards shall drain to an approved place of disposal. For one- and two-family dwellings, and where approved, storm water is permitted to discharge onto flat areas, such as streets or lawns, provided that the storm water flows away from the building.

Exception. Rainwater nonpotable water systems shall be permitted in accordance with Chapter 13.
Storm water shall not be drained into sewers intended for sewage only.
The conductors and the building storm drain shall be tested in accordance with Section 312.
The size of a drainage pipe shall not be reduced in the direction of flow.
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 retard flow in the system.
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 with 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 secondary drainage means to accommodate the design rainfall rate as required by Section 1106.
Cleanouts shall be installed in the storm drainage system and shall comply with the provisions of this code for sanitary drainage pipe cleanouts.

Exception: Subsurface drainage system.
Storm drainage systems shall be provided with backwater valves as required for sanitary drainage systems in accordance with Section 715.
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.
Inside storm drainage conductors installed above ground shall conform to one of the standards listed in Table 702.1.
Underground building storm drain pipe shall conform to one of the standards listed in Table 702.2.
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
Acrylonitrile butadiene styrene (ABS) plastic pipe ASTM D 2661; ASTM D 2751; ASTM F 628; CSA B181.1; CSA B182.1
Cast-iron pipe ASTM A 74; ASTM A 888; CISPI 301
Concrete pipe ASTM C 14; ASTM C 76;
CSA A257.1M; CSA A257.2M
Copper or copper-alloy tubing (Type K, L, M or DWV) ASTM B 75; ASTM B 88; ASTM B 251; ASTM B 306
Polyethylene (PE) plastic pipe ASTM F 2306/F 2306M
Polyvinyl chloride (PVC) plastic pipe (Type DWV, SDR26, SDR35, SDR41, PS50 or PS100) ASTM D 2665; ASTM D 3034; ASTM F 891; CSA B182.4; CSA B181.2; CSA B182.2
Vitrified clay pipe ASTM C 4; ASTM C 700
Stainless steel drainage systems, Type 316L ASME A112.3.1
Subsoil drains shall be openjointed, 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
Polyvinyl chloride (PVC)
Plastic pipe (type sewer pipe,
SDR35, PS25, PS50 or PS100)
ASTM D 2729; ASTM D 3034,
ASTM F 891; CSA B182.2; CSA
B182.4
Stainless steel drainage systems,
Type 316L
ASME A 112.3.1
Vitrified clay pipe ASTM C 4; ASTM C 700
Roof drains shall conform to ASME A112.6.4 or ASME A112.3.1.
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 FITTING 
MATERIAL STANDARD
Acrylonitrile butadiene styrene (ABS) plastic ASTM D 2661; ASTM D 3311; CSA B181.1
Cast-iron ASME B16.4; ASME B16.12; ASTM A 888; CISPI 301; ASTM A 74
Coextruded composite ABS and drain DR-PS in PS35, PS50, PS100, PS140, PS200 ASTM D 2751
Coextruded composite ABS DWV Schedule 40 IPS pipe (solid or cellular core) ASTM D 2661; ASTM D 3311; ASTM F 628
Coextruded composite PVC DWV Schedule 40 IPS-DR, PS140, PS200 (solid or cellular core) ASTM D 2665; ASTM D 3311; ASTM F 891
Coextruded composite PVC sewer and drain DR-PS in PS35, PS50, PS100, PS140, PS200 ASTM D 3034
Copper or copper alloy ASME B16.15; ASME B16.18; ASME B16.22; ASME B16.23; ASME B16.26; ASME B16.29
Gray iron and ductile iron AWWA C110/A21.10
Malleable iron ASME B16.3
Plastic, general ASTM F 409
Polyethylene (PE) plastic pipe ASTM F 2306/F 2306M
Polyvinyl chloride (PVC) plastic ASTM D 2665; ASTM D 3311; ASTM F 1866
Steel ASME B16.9; ASME B16.11; ASME B16.28
Stainless steel drainage systems, Type 316L ASME A112.3.1
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 connection with the combined building sewer or the public sewer. Leaders and storm drains connected to a building storm sewer shall not be required to be trapped.
Storm water traps shall be of the same material as the piping system to which they are attached.
Traps for individual conductors shall be the same size as the horizontal drain to which they are connected.
An accessible cleanout shall be installed on the building side of the trap.
Conductor pipes shall not be used as soil, waste or vent pipes, and soil, waste or vent pipes shall not be used as conductors.
Floor drains shall not be connected to a storm drain.
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.
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.
The size of the vertical conductors and leaders, 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 indicated in Figure 1106.1 or on other rainfall rates determined from approved local weather data.


For SI: 1 inch = 25.4 mm.
Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1
100-YEAR, 1-HOUR RAINFALL (INCHES) EASTERN UNITED STATES


For SI: 1 inch = 25.4 mm.
Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued
100-YEAR, 1-HOUR RAINFALL (INCHES) CENTRAL UNITED STATE


For SI: 1 inch = 25.4 mm.
Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued
100-YEAR, 1-HOUR RAINFALL (INCHES) WESTERN UNITED STATES

For SI: 1 inch = 25.4 mm.
Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued
100-YEAR, 1-HOUR RAINFALL (INCHES) ALASKA

For SI: 1 inch = 25.4 mm.
Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington D.C.
FIGURE 1106.1—continued
100-YEAR, 1-HOUR RAINFALL (INCHES) HAWAII

1106.2 Size of Storm Drain Piping

AMENDMENT
This section has been amended at the state or city level.

1106.2 Vertical Conductors and Leaders

AMENDMENT
This section has been amended at the state or city level.
Vertical conductors and leaders shall be sized for the maximum projected roof area, in accordance with Table 1106.2(1) and 1106.2(2).

TABLE 1106.2(1)
SIZE OF CIRCULAR VERTICAL CONDUCTORS AND LEADERS
DIAMETER OF
LEADER
(inches)a
HORIZONTALLY PROJECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
1 2 3 4 5 6 7 8 9 10 11 12
2 2,880 1,440 960 720 575 480 410 360 320 290 260 240
3 8,800 4,400 2,930 2,200 1,760 1,470 1,260 1,100 980 880 800 730
4 18,400 9,200 6,130 4,600 3,680 3,070 2,630 2,300 2,045 1,840 1,675 1,530
5 34,600 17,300 11,530 8,650 6,920 5,765 4,945 4,325 3,845 3,460 3,145 2,880
6 54,000 27,000 17,995 13,500 10,800 9,000 7,715 6,750 6,000 5,400 4,910 4,500
8 116,000 58,000 38,660 29,000 23,200 19,315 16,570 14,500 12,890 11,600 10,545 9,600
For SI: 1 inch = 25.4, 1 square foot = 0.0929 m2.
  1. Sizes indicated are diameter of circular piping. This table is applicable to piping of other shapes, provided the crosssectional shape fully encloses a circle of the diameter indicated in this table. For rectangular leaders, see Table 1106.2(2). Interpolation is permitted fo pipe sizes that fall between those listed in this table.
TABLE 1106.2(2)
SIZE OF RECTANGULAR VERTICAL CONDUCTORS AND LEADERS
DIMENSIONS
OF
COMMON
LEADER SIZES
width x length
(inchesa, b)
HORIZONTALLY PROJECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
1 2 3 4 5 6 7 8 9 10 11 12
1 3/4 × 2 1/2 3,410 1,700 1,130 850 680 560 480 420 370 340 310 280
2 × 3 5,540 2,770 1,840 1,380 1,100 920 790 690 610 550 500 460
2 3/4 × 4 1/4 12,830 6,410 4,270 3,200 2,560 2,130 1,830 1,600 1,420 1,280 1,160 1,060
3 × 4 13,210 6,600 4,400 3,300 2,640 2,200 1,880 1,650 1,460 1,320 1,200 1,100
3 1/2 × 4 15,900 7,950 5,300 3,970 3,180 2,650 2,270 1,980 1,760 1,590 1,440 1,320
3 1/2 × 5 21,310 10,650 7,100 5,320 4,260 3,550 3,040 2,660 2,360 2,130 1,930 1,770
3 3/4 × 4 3/4 21,960 10,980 7,320 5,490 4,390 3,660 3,130 2,740 2,440 2,190 1,990 1,830
3 3/4 × 5 1/4 25,520 12,760 8,500 6,380 5,100 4,250 3,640 3,190 2,830 2,550 2,320 2,120
3 1/2 × 6 27,790 13,890 9,260 6,940 5,550 4,630 3,970 3,470 3,080 2,770 2,520 2,310
4 × 6 32,980 16,490 10,990 8,240 6,590 5,490 4,710 4,120 3,660 3,290 2,990 2,740
5 1/2 × 5 1/2 44,300 22,150 14,760 11,070 8,860 7,380 6,320 5,530 4,920 4,430 4,020 3,690
7 1/2 × 7 1/2 100,500 50,250 33,500 25,120 20,100 16,750 14,350 12,560 11,160 10,050 9,130 8,370
For SI: 1 inch = 25.4, 1 square foot = 0.0929 m2.
  1. Sizes indicated are nominal width x length of the opening for rectangular piping.
  2. For shapes not included in this table, Equation 11-1 shall be used to determine the equivalent circular diameter, De, of rectangular piping for use in interpolation using the data from Table 1106.2(1).
De = [width x length]1/2 (Equation 11-1)

Where:
De = equivalent circular diameter and De, width and length are inches.

1106.3 Vertical Leader Sizing

AMENDMENT
This section has been amended at the state or city level.

1106.3 Building Storm Drains and Sewers

AMENDMENT
This section has been amended at the state or city level.
The size of the building storm drain, building storm sewer and their horizontal branches having a slope of one-half unit or less vertical in 12 units horizontal (4-percent slope) shall be based on the maximum projected roof area in accordance with Table 1106.3. The slope of horizontal branches shall be not less than one-eighth unit vertical in 12 units horizontal (1-percent slope) unless otherwise approved.

TABLE 1106.3
SIZE OF HORIZONTAL STORM DRAINAGE PIPING


SIZE OF
HORIZONTAL
PIPING
(inches)
HORIZONTALLY PROTECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
1 2 3 4 5 6
1/8 unit vertical in 12 units horizontal (1-percent slope)
3 3,288 1,644 1,096 822 657 548
4 7,520, 3,760 2,506 1,800 1,504 1,253
5 13,360 6,680 4,453 3,340 2,672 2,227
6 21,400 10,700 7,133 5,350 4,280 3,566
8 46,000 23,000 15,330 11,500 9,200 7,600
10 82,800 41,400 27,600 20,700 16,580 13,800
12 133,200 66,600 44,400 33,300 26,650 22,200
15 218,000 109,000 72,800 59,500 47,600 39,650
1/4 unit vertical in 12 units horizontal (2-percent slope)
3 4,640 2,320 1,546 1,160 928 773
4 10,600 5,300 3,533 2,650 2,120 1,766
5 18,880 9,440 6,293 4,720 3,776 3,146
6 30,200 15,100 10,066 7,550 6,040 5,033
8 65,200 32,600 21,733 16,300 13,040 10,866
10 116,800 58,400 38,950 29,200 23,350 19,450
12 188,000 94,000 62,600 47,000 37,600 31,350
15 336,000 168,000 112,000 84,000 67,250 56,000
(continued)

TABLE 1106.3
SIZE OF HORIZONTAL STORM DRAINAGE PIPING—continued


SIZE OF
HORIZONTAL
PIPING
(inches)
HORIZONTALLY PROTECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
1 2 3 4 5 6
1/2 unit vertical in 12 units horizontal (4-percent slope)
3 6,576 3,288 2,295 1,644 1,310 1,096
4 15,040 7,520 5,010 3,760 3,010 2,500
5 26,720 13,360 8,900 6,680 5,320 4,450
6 42,800 21,400 13,700 10,700 8,580 7,140
8 92,000 46,000 30,650 23,000 18,400 15,320
10 171,600 85,800 55,200 41,400 33,150 27,600
12 266,400 133,200 88,800 66,600 53,200 44,400
15 476,000 238,000 158,800 119,000 95,300 79,250
For SI: 1 inch = 25.4, 1 square foot = 0.0929 m2
In sizing roof drains and storm drainage piping, one-half of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.
Parapet wall roof drainage scupper and overflow scupper location shall comply with the requirements of Section 1503.4 of the International Building Code.

1106.6 Size of Roof Gutters

AMENDMENT
This section has been amended at the state or city level.
The size of semicircular gutters shall be based on the maximum projected roof area in accordance with Table 1106.6.

TABLE 1106.6
SIZE OF SEMICIRCULAR ROOF GUTTERS


SIZE OF
HORIZONTAL
PIPING
(inches)
HORIZONTALLY PROTECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
1 2 3 4 5 6
1/16 unit vertical in 12 units horizontal (0.5-percent slope)
3 680 340 226 170 136 113
4 1,440 720 480 360 288 240
5 2,500 1,250 834 625 500 416
6 3,840 1,920 1,280 960 768 640
7 5,520 2,760 1,840 1,380 1,100 918
8 7,960 3,980 2,655 1,990 1,590 1,325
10 14,400 7,200 4,800 3,600 2,880 2,400
1/8 unit vertical in 12 units horizontal (1-percent slope)
3 960 480 320 240 192 160
4 2,040 1,020 681 510 408 340
5 3,520 1,760 1,172 880 704 587
6 5,440 2,720 1,815 1,360 1,085 905
7 7,800 3,900 2,600 1,950 1,560 1,300
8 11,200 5,600 3,740 2,800 2,240 1,870
10 20,400 10,200 6,800 5,100 4,080 3,400
1/4 unit vertical in 12 units horizontal (2-percent slope)
3 1,360 680 454 340 272 226
4 2,880 1,440 960 720 576 480
5 5,000 2,500 1,668 1,250 1,000 834
6 7,680 3,840 2,560 1,920 1,536 1,280
7 11,040 5,520 3,860 2,760 2,205 1,840
8 15,920 7,960 5,310 3,980 3,180 2,655
10 28,800 14,400 9,600 7,200 5,750 4,800
1/2 unit vertical in 12 units horizontal (4-percent slope)
3 1,920 960 640 480 384 320
4 4,080 2,040 1,360 1,020 816 680
5 7,080 3,540 2,360 1,770 1,415 1,180
6 11,080 5,540 3,695 2,770 2,220 1,850
7 15,600 7,800 5,200 3,900 3,120 2,600
8 22,400 11,200 7,460 5,600 4,480 3,730
10 40,000 20,000 13,330 10,000 8,000 6,660
For SI: 1 inch = 25.4, 1 square foot = 0.0929 m2
Siphonic roof drains and drainage systems shall be designed in accordance with ASME A112.6.9 and ASPE 45.
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. Where primary and secondary roof drains are manufactured as a single assembly, the inlet and outlet for each drain shall be independent.
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.
Secondary (emergency) roof drain systems shall be sized in accordance with Section 1106 based on the rainfall rate for which the primary system is sized. Scuppers 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 system shall not be considered when sizing the secondary roof drain system.
Where the public sewer is a combined system for both sanitary and storm water, the storm sewer shall be connected independently to the public sewer.
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 section and the design, submittal, approval, inspection and testing requirements of Section 316.1. The controlled flow system shall be designed based on the required rainfall rate in accordance with Section 1106.1.
The control devices shall be installed so that the rate of discharge of water per minute shall not exceed the values for continuous flow as indicated in Section 1110.1.
Runoff control shall be by control devices. Control devices shall be protected by strainers.
Not less than two roof drains shall be installed in roof areas 10,000 square feet (929 m2) or less and not less than four roof drains shall be installed in roofs over 10,000 square feet (929 m2) in area.
Subsoil drains 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 drains shall discharge to a trapped area drain, sump, dry well or approved location above ground. The subsoil sump 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.
Building subdrains located below the public sewer level shall discharge 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.
The sump pump, pit and discharge piping shall conform to Sections 1113.1.1 through 1113.1.4.
The sump pump shall be of a capacity and head appropriate to anticipated use requirements.
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.
Electrical service outlets, when required, shall meet the requirements of NFPA 70.
Discharge piping shall meet the requirements of Section 1102.2, 1102.3 or 1102.4 and shall include a gate valve 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 ejector.
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