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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 12. CONSTRUCTION CODES SUPPLEMENT OF 2013 |
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SubTilte 12-F. PLUMBING CODE SUPPLEMENT OF 2013 |
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Chapter 12-F11. STORM DRAINAGE |
Section 12-F1115. RAINWATER COLLECTION AND DISTRIBUTION SYSTEMS
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Insert new Section 1115 in the Plumbing Code to read as follows:
1115.1 Scope. 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.
1115.2 Potable water connections. 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.
1115.3 Nonpotable water connections. 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. 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.
1115.5 Rainwater collected for landscape irrigation. 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.
1115.6 Approved components and materials. 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.
1115.7 Insect and vermin control. 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 1/16 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. 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 discharge 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. Where sustained freezing temperatures occur, provisions shall be made to keep storage tanks and the related piping from freezing.
1115.10 Trenching requirements. 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.
1115.11 Rainwater catchment and collection systems. The design of rainwater collection and conveyance systems shall conform to accepted engineering practice.
1115.11.1 Collection surface. 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. 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.
1115.11.3 Roof gutters and downspouts. 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. 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. Gutters and downspouts shall be installed and sized in accordance with Section 1106.6.
1115.11.3.3 Cleanouts. Cleanouts shall be provided in the water conveyance system so as to allow access to all filters, flushes, pipes and downspouts.
1115.11.4 Collection pipe materials. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.
1115.11.7.9 Draining of tanks. 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.
1115.11.7.10 Marking and signage. 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 0.5 inches (13 mm) in height and shall be of a color that contrasts with the background on which they are applied.
1115.11.8 Valves. Valves shall be installed in accordance with Section 1115.11.8.1.
1115.11.8.1 Backwater valve. 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. 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. 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.
1115.11.11 Pumping and control system. 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.
1115.11.11.1 Water-pressure-reducing valve or regulator. 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.
1115.11.12 Distribution pipe. Distribution piping shall comply with Sections 1115.11.12.1 through 1115.11.12.4.
1115.11.12.1 Materials. Distribution piping conveying rainwater shall conform to the standards and requirements specified by the Plumbing Code for nonpotable water.
1115.11.12.2 Joints. 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. Distribution piping conveying rainwater shall be sized in accordance with the Plumbing Code for the intended application.
1115.11.12.4 Marking. 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 preventer is not required to be purple where rainwater is used for outdoor applications.
1115.12 Tests and inspections. Tests and inspections shall be performed in accordance with Sections 1115.12.1 through 1115.12.10.
1115.12.1 Drainage and vent tests. The testing of rainwater collection piping, overflow piping, vent piping and storage tank drains shall be conducted in accordance with Section 312.
1115.12.2 Draining and vent final test. 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.
1115.12.3 Water supply system test. The testing of makeup water supply piping and rainwater distribution piping shall be conducted in accordance with Section 312.5.
1115.12.4 Inspection and testing of backflow prevention assemblies. The testing of backflow preventers and backwater valves shall be conducted in accordance with Section 312.10.
1115.12.5 Inspection of vermin and insect protection. 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.
1115.12.6 Roof gutter inspection. 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. 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.
1115.12.8 Storage tank tests. 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.
1115.12.9 Supply pressure test. 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.
1115.12.10 Water quality test. 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.
1115.13 Operations and maintenance manuals. Operations and maintenance materials shall be supplied by the installer to the owner of the system in accordance with 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. A detailed operations and maintenance manual shall be supplied in hardcopy form with all rainwater collection systems.
1115.13.2 Schematics. 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.
1115.13.3 Maintenance procedures. 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.
1115.13.4 Operations procedures. The manual shall include system startup and shutdown procedures. The manual shall include detailed operating procedures for the system.
1115.14 System abandonment. 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:
- 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.
- 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.
1115.14.1 Mandatory abandonment. 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.