CODES

ADOPTS WITH AMENDMENTS:

International Plumbing Code 2012 (IPC 2012)

Chapter 1 Scope and Administration

Chapter 1 SCOPE AND ADMINISTRATION

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Fixtures, Faucets and Fixture Fittings

Chapter 5 Water Heaters

Chapter 6 Water Supply and Distribution

Chapter 7 Sanitary Drainage

Chapter 8 Indirect/Special Waste

Chapter 9 Vents

Chapter 10 Traps, Interceptors and Separators

Chapter 11 Storm Drainage

Chapter 12 Special Piping and Storage Systems

Chapter 13 Gray Water Recycling Systems

Chapter 14 Referenced Standards

Appendix A Plumbing Permit Fee Schedule

Appendix B Rates of Rainfall for Various Cities

Appendix C Vacuum Drainage System

Appendix D Degree Day and Design Temperatures

Appendix E Sizing of Water Piping System

Appendix F Structural Safety

The provisions of this chapter shall govern the materials, design, construction and installation of storm drainage.

1101.2 Where Required

STATE AMENDMENT
All roofs, paved areas, yards, courts and courtyards shall drain into a separate storm sewer system, or a combined sewer system, or 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: When approved, storm water is permitted to be discharged from roofs, paved areas, yards, courts, courtyards, downspouts, rain barrels, cisterns or rooftop storage facilities to vegetated areas such as lawns, gardens, grassy swales or bio-retention cells on the same lot. In such instances, the storm water shall flow away from the building and shall not flow across property lines onto adjacent lots unless it discharges into an approved shared best management practice as defined in 21 DCMR Chapter 5.
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.
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

MATERIALSTANDARD
Acrylonitrile butadiene
styrene (ABS) plastic pipe
ASTM D 2661; ASTM D 2751; ASTM F 628; CSA B181.1;
CSA B182.1
Asbestos-cement pipeASTM C 428
Cast-iron pipeASTM 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 pipeASTM 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 pipeASTM C 4; ASTM C 700
Stainless steel drainage
systems, Type 316L
ASME A112.3.1
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

MATERIALSTANDARD
Asbestos-cement pipe ASTM C 508
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,
PS25, PS50 or PS100)
ASTM D 2729; ASTM F 891; CSA B182.2; CSA B182.4
Stainless steel drainage systems,
Type 316L
ASME A 112.3.1
Vitrified clay pipeASTM 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

MATERIALSTANDARD
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 alloyASME B16.15; ASME B16.18; ASME B16.22; ASME B16.23; ASME B16.26; ASME B16.29
Gray iron and ductile ironAWWA C110/A21.10
Malleable ironASME B16.3
Plastic, generalASTM F 409
Polyethylene (PE) plastic pipeASTM F 2306/F 2306M
Polyvinyl chloride (PVC)
plastic
ASTM D 2665; ASTM D 3311; ASTM F 1866
SteelASME 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.
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.
The sanitary and storm drainage systems of a structure shall be entirely separate except where the structure is served by a combined sewer systems are utilized.The storm building drain and the sanitary building drain shall remain separate through the exterior walls of the building. Where a combined public sewer is utilized, the building storm drain shall be connected in the same horizontal plane through a single-wye fitting to the combined sewer, not less than 10 feet (3048 mm) downstream from any soil stack, and downstream of any backwater valve. Where the connection is in public space or when the size of either drain is 8 inches in diameter or larger, the combination shall be made with a manhole in lieu of a single-wye..
Floor drains shall not be connected to a storm drain.
Deleted
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.

Deleted

The connection between roofs and roof drains which pass through the roof and into the interior of the building shall be made water-tight by the use of approved flashing material.
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 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) 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

Vertical conductors and leaders shall be sized for the maximum projected roof area, in accordance with Table 1106.2(1) and Table 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)
123456789101112
22,8801,440960720575480410360320290260240
38,8004,4002,9302,2001,7601,4701,2601,100980880800730
418,4009,2006,1304,6003,6803,0702,6302,3002,0451,8401,6751,530
534,60017,30011,5308,6506,9205,7654,9454,3253,8453,4603,1452,880
654,00027,00017,99513,50010,8009,0007,7156,7506,0005,4004,9104,500
8116,00058,00038,66029,00023,20019,31516,57014,50012,89011,60010,5459,600
For SI: 1 inch = 25.4 mm, 1 square foot = 0.0929 m2.
a. Sizes indicated are the diameter of circular piping. This table is applicable to piping of other shapes, provided the cross-sectional shape fully encloses a circle of the diameter indicated in this table. For rectangular leaders, see Table 1106.2(2). Interpolation is permitted for 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 (inches)a, b
HORIZONTALLY PROJECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
123456789101112
13/4 × 21/23,4101,7001,130850680560480420370340310280
2 × 35,5402,7701,8401,3801,100920790690610550500460
23/4 × 41/412,8306,4104,2703,2002,5602,1301,8301,6001,4201,2801,1601,060
3 × 413,2106,6004,4003,3002,6402,2001,8801,6501,4601,3201,2001,100
31/2 × 415,9007,9505,3003,9703,1802,6502,2701,9801,7601,5901,4401,320
31/2 × 521,31010,6507,1005,3204,2603,5503,0402,6602,3602,1301,9301,770
33/4 × 43/421,96010,9807,3205,4904,3903,6603,1302,7402,4402,1901,9901,830
33/4 × 51/425,52012,7608,5006,3805,1004,2503,6403,1902,8302,5502,3202,120
31/2 × 627,79013,8909,2606,9405,5504,6303,9703,4703,0802,7702,5202,310
4 × 632,98016,49010,9908,2406,5905,4904,7104,1203,6603,2902,9902,740
51/2 × 51/244,30022,15014,76011,0708,8607,3806,3205,5304,9204,4304,0203,690
71/2 × 71/2100,50050,25033,50025,12020,10016,75014,35012,56011,16010,0509,1308,370
For SI: 1 inch = 25.4 mm, 1 square foot = 0.0929 m2.
a. Sizes indicated are nominal width × length of the opening for rectangular piping.
b. 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 × length]1/2
(Equation 11-1)
where:
De=equivalent circular diameter and De, width and length are in inches.
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 DRAINGE PIPING

SIZE OF
HORIZONTAL
PIPING
(inches)
HORIZONTALLY PROJECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
123456
1/8 unit vertical in 12 units horizontal (1-percent slope)
3
4
5
6
8
10
12
15
3,288
7,520
13,360
21,400
46,000
82,800
133,200
218,000
1,644
3,760
6,680
10,700
23,000
41,400
66,600
109,000
1,096
2,506
4,453
7,133
15,330
27,600
44,400
72,800
822
1,800
3,340
5,350
11,500
20,700
33,300
59,500
657
1,504
2,672
4,280
9,200
16,580
26,650
47,600
548
1,253
2,227
3,566
7,600
13,800
22,200
39,650
1/4 unit vertical in 12 units horizontal (2-percent slope)
3
4
5
6
8
10
12
15
4,640
10,600
18,880
30,200
65,200
116,800
188,000
336,000
2,320
5,300
9,440
15,100
32,600
58,400
94,000
168,000
1,546
3,533
6,293
10,066
21,733
38,950
62,600
112,000
1,160
2,650
4,720
7,550
16,300
29,200
47,000
84,000
928
2,120
3,776
6,040
13,040
23,350
37,600
67,250
773
1,766
3,146
5,033
10,866
19,450
31,350
56,000
1/2 unit vertical in 12 units horizontal (4-percent slope)
3
4
5
6
8
10
12
15
6,576
15,040
26,720
42,800
92,000
171,600
266,400
476,000
3,288
7,520
13,360
21,400
46,000
85,800
133,200
238,000
2,295
5,010
8,900
13,700
30,650
55,200
88,800
158,800
1,644
3,760
6,680
10,700
23,000
41,400
66,600
119,000
1,310
3,010
5,320
8,580
18,400
33,150
53,200
95,300
1,096
2,500
4,450
7,140
15,320
27,600
44,400
79,250
For SI: 1 inch = 25.4 mm, 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 CodeBuilding Code.
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

DIAMETER OF
GUTTERS
(inches)
HORIZONTALLY PROJECTED ROOF AREA (square feet)
Rainfall rate (inches per hour)
123456
1/16 unit vertical in 12 units horizontal (0.5-percent slope)
3
4
5
6
7
8
10
680
1,440
2,500
3,840
5,520
7,960
14,400
340
720
1,250
1,920
2,760
3,980
7,200
226
480
834
1,280
1,840
2,655
4,800
170
360
625
960
1,380
1,990
3,600
136
288
500
768
1,100
1,590
2,880
113
240
416
640
918
1,325
2,400
1/8 unit vertical 12 units horizontal (1-percent slope)
3
4
5
6
7
8
10
960
2,040
3,520
5,440
7,800
11,200
20,400
480
1,020
1,760
2,720
3,900
5,600
10,200
320
681
1,172
1,815
2,600
3,740
6,800
240
510
880
1,360
1,950
2,800
5,100
192
408
704
1,085
1,560
2,240
4,080
160
340
587
905
1,300
1,870
3,400
1/4 unit vertical in 12 units horizontal (2-percent slope)
3
4
5
6
7
8
10
1,360
2,880
5,000
7,680
11,040
15,920
28,800
680
1,440
2,500
3,840
5,520
7,960
14,400
454
960
1,668
2,560
3,860
5,310
9,600
340
720
1,250
1,920
2,760
3,980
7,200
272
576
1,000
1,536
2,205
3,180
5,750
226
480
834
1,280
1,840
2,655
4,800
1/2 unit vertical in 12 units horizontal (4-percent slope)
3
4
5
6
7
8
10
1,920
4,080
7,080
11,080
15,600
22,400
40,000
960
2,040
3,540
5,540
7,800
11,200
20,000
640
1,360
2,360
3,695
5,200
7,460
13,330
480
1,020
1,770
2,770
3,900
5,600
10,000
384
816
1,415
2,220
3,120
4,480
8,000
320
680
1,180
1,850
2,600
3,730
6,660
For SI: 1 inch = 25.4 mm, 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.
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 in Tables 1106.2(1), 1106.2(2), 1106.3 and 1106.6. 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.
The size of a combination sanitary and storm drain or sewer shall be computed in accordance with the method in Section 1106.3. The fixture units shall be converted into an equivalent projected 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 4,000 square feet (372 m2). Where the total fixture load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 15.6 square feet (1.5 m2) of drainage area. These values are based on a rainfall rate of 1 inch (25 mm) per hour.
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 (L/m) of such discharge shall be computed as being equivalent to 96 square feet (9 m2) of roof area, based on a rainfall rate of 1 inch (25.4 mm) per hour.
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 1114.1.
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 1114.1.
The sump pump, pit and discharge piping shall conform to Sections 1114.1.1 through 1114.1.4.
The sump pump shall be of a capacity and head appropriate to anticipated use requirements.
The sump pit shall not be 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, 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.

1115.1 Scope

STATE AMENDMENT
The provisions of this section shall govern the construction, installation, alteration and repair of rainwater collection and conveyance systems. Water collected in rainwater collection systems shall not be used as drinking water or for any other potable water application.
Where a potable system is connected to a rainwater collection and conveyance system, the potable water supply shall be protected against backflow by an approved air gap fitting in accordance with Section 608.13.1.
Nonpotable water from any source other than roof drainage, other storm drainage or condensate water where approved shall not be combined in a rainwater collection and distribution system.

1115.4 Installation

STATE AMENDMENT
Except as provided for in this section, all systems shall be installed in compliance with the provisions of the Plumbing Code and the manufacturer’s instructions.
Rainwater collected on the surface of the building site, or from the roof surfaces of the building, and used for landscape irrigation purposes shall not be limited regarding the method of application. Rainwater collected from elevated building locations that is to be used in building site irrigation shall comply with the provisions of Section 1115 with the exception of Sections 1115.11.1 and 1115.11.7.3.
Piping, plumbing components, and materials used in the collection and conveyance systems shall be manufactured of material approved for the intended application and compatible with any disinfection and treatment systems used.
Inlets and vents to the system shall be protected to prevent the entrance of insects and vermin into storage tanks and piping systems. Screens installed on vent pipes, inlets, and overflow pipes shall have an aperture of not greater than 116 inch (1.6 mm) and shall be close fitting. Screen materials shall be compatible with contacting system components and shall not accelerate corrosion of system components.

1115.8 Drainage

STATE AMENDMENT
Water drained from the roof washer or debris excluder shall not be drained to the sanitary sewer. Such water shall be diverted from the storage tank and discharged in a location that will not cause erosion or damage to property. Roof washers and debris excluders shall be provided with an automatic means of self-draining between rain events, and shall not drain onto roof surfaces.

1115.9 Freeze protection

STATE AMENDMENT
Where sustained freezing temperatures occur, provisions shall be made to keep storage tanks and the related piping from freezing.
All collection and distribution piping containing rainwater shall be separated from the building sewer as required in Section 603.2 for water service piping.

Exception: Irrigation piping located outside of a building and downstream of the backflow preventer is not required to meet the trenching requirements where rainwater is used for outdoor applications.
The design of rainwater collection and conveyance systems shall conform to accepted engineering practice.
Rainwater shall be collected only from above-ground impervious roofing surfaces constructed from approved materials. Collection of water from vehicular parking, pedestrian, or other surfaces shall be prohibited except where the water is used exclusively for landscape irrigation or where water quality treatment measures that are adequate for the end use have been approved. Overflow and bleed-off pipes from roof-mounted appliances including but not limited to evaporative coolers, water heaters and solar water heaters shall not discharge onto rainwater collection surfaces.

1115.11.2 Debris excluders

STATE AMENDMENT
Downspouts and leaders shall be connected to a roof washer and shall be equipped with a debris excluder or equivalent device to prevent the contamination of collected rainwater with leaves, sticks, pine needles and similar material. Debris excluders and equivalent devices shall be self-cleaning.
Gutters and downspouts shall be constructed of materials that are compatible with the collection surface and the rainwater quality for the desired end use. Joints shall be watertight.

1115.11.3.1 Slope

STATE AMENDMENT
Roof gutters, leaders and rainwater collection piping shall slope continuously toward collection inlets. Gutters and downspouts shall have a slope of not less than 1 unit in 96 units along their entire length and shall not permit the collection or pooling of water at any point.

Exception: Siphonic drainage systems installed in accordance with the manufacturer’s installation instructions shall not be required to have slope.

1115.11.3.2 Size

STATE AMENDMENT
Gutters and downspouts shall be installed and sized in accordance with Section 1106.6.

1115.11.3.3 Cleanouts

STATE AMENDMENT
Cleanouts shall be provided in the water conveyance system so as to allow access to all filters, flushes, pipes and downspouts.
In buildings where rainwater collection and conveyance systems are installed, draining piping approved for use within plumbing draining systems shall be utilized to collect rainwater and convey it to the storage tank.Vent piping approved for use within plumbing venting systems shall be utilized for all vents within the rainwater system. Drains to a stormwater discharge shall use approved waste piping.

1115.11.4.1 Joints

STATE AMENDMENT
Collection piping conveying rainwater shall utilize joints approved for use with the distribution piping and appropriate for the intended applications as specified in the Plumbing Code.

1115.11.4.2 Size

STATE AMENDMENT
Collection piping conveying rainwater from collection surfaces shall be sized in accordance with Chapter 11 of the Plumbing Code and local rainfall rates.

1115.11.4.3 Marking

STATE AMENDMENT
Additional marking of rainwater collection piping shall not be required beyond that required for sanitary drainage, waste and vent piping by the Plumbing Code.

1115.11.5 Filtration

STATE AMENDMENT
Collected rainwater shall be filtered to the level required for the intended end use. Filters shall be accessible for inspection and maintenance.

1115.11.6 Disinfection

STATE AMENDMENT
Where the intended application and initial quality of the collected rainwater requires disinfection or other treatment, or both, the collected rainwater shall be treated as needed to ensure that the required water quality is delivered at the point of use. Where chlorine is used for disinfection or treatment, water shall be tested for residual chlorine in accordance with ASTM D 1253. The levels of residual chlorine shall not exceed the levels allowed for the intended use in accordance with the requirements of the District of Columbia.

1115.11.7 Storage tank

STATE AMENDMENT
The design of the storage tank shall be in accordance with Sections 1115.11.7.1 through 1115.11.7.10.

1115.11.7.1 Location

STATE AMENDMENT
Storage tanks shall be installed either above or below grade. Above-grade storage tanks shall be protected from direct sunlight and shall be constructed using opaque, UV-resistant materials including, but not limited to, heavily tinted plastic, fiberglass, lined metal, concrete, wood or painted to prevent algae growth, or shall have specially constructed sun barriers including, but not limited to, installation in garages, crawlspaces or sheds. Storage tanks and their manholes shall not be located directly under any soil or waste piping or any source of contamination. Rainwater storage tanks shall be located with a minimum horizontal distance between various elements as indicated in Table 1115.11.7.1.

TABLE 1115.11.7.1
LOCATION OF RAINWATER STORAGE TANKS
ELEMENT MINIMUM HORIZONTAL
DISTANCE FROM STORAGE TANK
(FEET)
Critical root zone (CRZ) of protected trees 2
Lot line adjoining private lots 5
Seepage pits 5
For SI: 1 foot = 304.8 mm.

1115.11.7.2 Materials

STATE AMENDMENT
Where water is collected onsite, it shall be collected in an approved tank constructed of durable, nonabsorbent and corrosion-resistant materials. Storage vessels shall be compatible with the material being stored. Storage tanks shall be constructed of materials compatible with the type of disinfection system used to treat water upstream of the tank and used to maintain water quality within the tank.

1115.11.7.2.1 Wooden tanks

STATE AMENDMENT
Wooden storage tanks shall not be required to have a liner. Where unlined tanks are used, the species of wood shall be decay resistant and untreated.

1115.11.7.3 Makeup water

STATE AMENDMENT
Where an uninterrupted supply is required for the intended application, potable water shall be provided as a source of make-up water for the storage tank. The potable water supply shall be protected against backflow by an approved air gap fitting in accordance with Section 608.13.1.

1115.11.7.4 Overflow

STATE AMENDMENT
The storage tank shall be equipped with an overflow pipe having the same or larger area as the sum of the areas of all tank inlet pipes. The overflow pipe shall be protected from insects or vermin, and the discharge from such pipe shall be disposed of in a manner consistent with stormwater runoff requirements of the District of Columbia. The overflow pipe shall discharge at a sufficient distance from the tank to avoid damaging the tank foundation or the adjacent property. The overflow drain shall not be equipped with a shutoff valve. A minimum of one cleanout shall be provided on each overflow pipe in accordance with Section 708.

1115.11.7.5 Access

STATE AMENDMENT
A minimum of one access opening shall be provided to allow inspection and cleaning of the tank interior. Access openings to storage tanks and other vessels shall have an approved locking device or shall otherwise be protected from unauthorized access. Below-grade storage tanks located outside of the building shall be provided with either a manhole not less than 24 inches (610 mm) square or a manhole with an inside diameter of not less than 24 inches (610 mm). Manholes shall extend not less than 4 inches (102 mm) above ground or shall be designed so as to prevent water infiltration. Finish grade shall be sloped away from the manhole to divert surface water from the manhole. Each manhole cover shall be secured to prevent unauthorized access. Service ports in manhole covers shall be not less than 8 inches (203 mm) in diameter and shall be not less than 4 inches (102 mm) above the finished grade level. The service port shall be secured to prevent unauthorized access.

Exception: Storage tanks having a volume of less than 800 gallons (3028 L) and installed below grade shall not be required to be equipped with a manhole where provided with a service port that is not less than 8 inches (203 mm) in diameter.

1115.11.7.6 Venting

STATE AMENDMENT
Storage tanks shall be provided with a vent sized in accordance with the Plumbing Code and based on the diameter of the tank influent pipe. Tank vents shall not be connected to sanitary drainage system vents.

1115.11.7.7 Inlets

STATE AMENDMENT
Storage tank inlets shall be designed to introduce water into the tank with minimum turbulence and shall be located and designed to avoid agitating the contents of the storage tank.

1115.11.7.8 Outlets

STATE AMENDMENT
Outlets shall be located not less than 4 inches (102 mm) above the bottom of the storage tanks and shall not skim water from the surface.
Where storage tanks require draining for service or cleaning, tanks shall be drained by using a pump or by a drain located at the lowest point in the tank. The discharge from draining the tank shall be disposed of in a manner consistent with the stormwater runoff requirements of the District of Columbia and at a sufficient distance from the tank to avoid damaging the tank foundation.
Each storage tank shall be marked with its rated capacity. Storage tanks shall bear signage that reads as follows: “CAUTION: NONPOTABLE WATER – DO NOT DRINK.” Where an opening is provided that could allow the entry of personnel, the opening shall bear signage that reads as follows: “DANGER – CONFINED SPACE.” Markings shall be indelibly printed on a tag or sign constructed of corrosion-resistant waterproof material mounted on the tank or shall be indelibly printed on the tank. The letters of words shall be not less than 12 inch (13 mm) in height and shall be of a color that contrasts with the background on which they are applied.

1115.11.8 Valves

STATE AMENDMENT
Valves shall be installed in accordance with Section 1115.11.8.1.

1115.11.8.1 Backwater valve

STATE AMENDMENT
Backwater valves shall be installed on each overflow and tank drain pipe. Backwater valves shall be installed so that access is provided to the working parts for service and repair.

1115.11.9 Roof washer

STATE AMENDMENT
A sufficient amount of rainwater shall be diverted at the beginning of each rain event, and not allowed to enter the storage tank, to wash accumulated debris from the collection surface, or approved pre-treatment measures shall be used as specified in a plan approved in compliance with 21 DCMR Chapter 5. The amount of rainfall to be diverted shall be field adjustable as necessary to minimize storage tank water contamination. The roof washer shall not rely on manually operated valves or devices, and shall not operate automatically. Diverted rainwater shall not be drained to the roof surface and shall be discharged in a manner consistent with the stormwater runoff requirements of the District of Columbia. Roof washers shall be accessible for maintenance and service.

1115.11.10 Vent piping

STATE AMENDMENT
Storage tanks shall be provided with a vent in accordance with the requirements of Section 1115.11.7.6. Vents shall be sized in accordance with the Plumbing Code, based on the aggregate diameter of storage tank influent pipe(s). Vents shall be protected from contamination by means of a U-bend installed with the opening directed downward or an approved cap. Vent outlets shall extend a minimum of 4 inches (102 mm) above grade or as necessary to prevent surface water from entering the storage tank. Vent openings shall be protected against the entrance of vermin and insects in accordance with the requirements of Section 1115.7.
Mechanical equipment including pumps, valves and filters shall be easily accessible and removable in order to perform repair, maintenance and cleaning. Pressurized water shall be supplied at a pressure appropriate for the application and within the range specified by the Plumbing Code. Where water could be supplied at an excessive pressure, a pressure- reducing valve shall be installed in accordance with the requirements of the Plumbing Code.
Where the rainwater pressure supplied by the pumping system exceeds 80 psi (552 kPa) static, a pressure-reducing valve shall be installed to reduce the pressure in the rainwater distribution system piping to 80 psi (552 kPa) static or less. Pressure-reducing valves shall be specified and installed in accordance with Section 604.8.
Distribution piping shall comply with Sections 1115.11.12.1 through 1115.11.12.4.

1115.11.12.1 Materials

STATE AMENDMENT
Distribution piping conveying rainwater shall conform to the standards and requirements specified by the Plumbing Code for nonpotable water.

1115.11.12.2 Joints

STATE AMENDMENT
Distribution piping conveying rainwater shall utilize joints approved for use with the distribution piping and appropriate for the intended applications as specified in the Plumbing Code.

1115.11.12.3 Size

STATE AMENDMENT
Distribution piping conveying rainwater shall be sized in accordance with the Plumbing Code for the intended application.

1115.11.12.4 Marking

STATE AMENDMENT
Nonpotable rainwater distribution piping shall be of the color purple and shall be embossed or indelibly printed with the words: “CAUTION: NONPOTABLE WATER – DO NOT DRINK” or shall be installed with a purple identification tape or wrap. Identification tape shall be not less than 3 inches (76 mm) wide and shall have white or black lettering on purple stating “CAUTION: NONPOTABLE WATER – DO NOT DRINK.” Identification tape shall be installed on top of nonpotable rainwater distribution pipes, fastened not greater than every 10 feet (3048 mm) to each pipe length and run continuously the entire length of the pipe. Lettering shall be readily observable within the room or space where the piping is located.

Exception: Piping located outside of the building and downstream of the backflow prevente is not required to be purple where rainwater is used for outdoor applications.
Tests and inspections shall be performed in accordance with Sections 1115.12.1 through 1115.12.10.
The testing of rainwater collection piping, overflow piping, vent piping and storage tank drains shall be conducted in accordance with Section 312.
A final test shall be applied to the rainwater collection piping, overflow piping, storage tank, and tank vent piping in accordance with Section 312.4.
The testing of makeup water supply piping and rainwater distribution piping shall be conducted in accordance with Section 312.5.
The testing of backflow preventers and backwater valves shall be conducted in accordance with Section 312.10.
Inlets and vents to the system shall be inspected to ensure that each is protected to prevent the entrance of insects or vermin into storage tank and piping systems in accordance with Section 1115.8.
Roof gutters shall be inspected to verify that the installation and slope is in accordance with Section 1115.11.3.

1115.12.7 Roofwasher test

STATE AMENDMENT
Roofwashers shall be tested by introducing water into the gutters. Proper diversion of the first quantity of water in accordance with the requirements of Section 1115.11.9 shall be verified.
Storage tanks shall be tested in accordance with the following:
  1. Storage tanks other than factory-made tanks shall be filled with water to the overflow line prior to and during inspection. Seams and joints shall be left exposed and the tank shall remain water tight without leakage for a period of 24 hours.
  2. The overflow system shall be tested for a period of 15 minutes to verify proper drainage and verify that there are no leaks.
  3. The makeup water system shall be tested for proper operation, and automatic shutoff of the system at the refill threshold shall be verified.
The static water pressure at the point of use farthest from the supply shall be verified to be within the range required for the application, in accordance with Section 1115.11.11.
The quality of the water for the intended application shall be verified at the point of use in accordance with all applicable requirements of the District of Columbia.
Operations and maintenance materials shall be supplied by the installer to the owner of the system in accordance with Sections 1115.13.1 through 1115.13.4. The owner shall keep these manuals on site or where they are readily available to the code official upon request.

1115.13.1 Manual

STATE AMENDMENT
A detailed operations and maintenance manual shall be supplied in hardcopy form with all rainwater collection systems.

1115.13.2 Schematics

STATE AMENDMENT
The manual shall include a detailed system schematic, the locations of all system components and a list of all system components including manufacturer and model number.
The manual shall provide a maintenance schedule and procedures for all system components requiring periodic maintenance. Consumable parts including filters shall be noted along with part numbers.
The manual shall include system startup and shutdown procedures. The manual shall include detailed operating procedures for the system.

1115.14 System abandonment

STATE AMENDMENT
In order to abandon or cease use of a rainwater collection and conveyance system, other than rain barrels, the owner shall first obtain approval for abandonment of the system from both the District Department of the Environment and the code official. Abandonment of a rainwater collection and conveyance system shall comply with the following:
  1. System piping connecting to a utility-provided water system shall be removed or disabled, and the potable water supply line shall be capped with an approved cap or plug.
  2. The storage tank shall be secured from inadvertent access by sealing or locking tank inlets and access points, or by filling with sand or by other equivalent approved method.
Mandatory abandonment of a rainwater collection and conveyance system is required where (1) system installation is not required by the stormwater requirements in 21 DCMR Chapter 5; and (2) the owner fails to properly maintain the system in accordance with the maintenance procedures set forth in Section 1115.13. The owner shall comply with the system abandonment procedures set forth in Section 1115.14.
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