Summary of District of Columbia’s Water Reuse Guideline or Regulation for Landscaping and Onsite Non-potable Water Reuse
This page is part of the EPA’s REUSExplorer tool, which summarizes the different state level regulations or guidelines for water reuse for a variety of sources and end-uses.
The source water for this summary is Rainwater Collected Onsite.
- Technical basis
- Onsite non-potable water reuse approved for use in District of Columbia
- Water reuse category/type
- Additional context and definitions
- Onsite non-potable reuse specifications (table)
- Upcoming state law or policy
- References
- Disclaimer
This page is a summary of the state’s water reuse law or policy and is provided for informational purposes only. Please always refer to the state for the most accurate and updated information.
In Washington District of Columbia (Washington, D.C.), landscaping and onsite non-potable water reuse applications include toilet and urinal flushing, exterior washing, fire suppression, cooling towers, water features and laundry. The source of water rainwater collected onsite Precipitation collected at the district or regional scale is classified separately under 'stormwater.' is specified by the state as rainwater. The write-up uses state terms when discussing sources or uses of water that may differ from the Regulations and End-Use Specifications Explorer's (REUSExplorer's) terms.
Technical basis
Washington District of Columbia approves the use of harvested rainwater for onsite non-potable water reuse applications (DCPC, 2017). All non-potable rainwater collection and distribution systems must abide by the minimum standards set by the D.C. Plumbing Code (DCPC, 2017). All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations, must be met in addition to any district-specific water quality standards. A permit is required for the construction, installation, repair, or alteration of non-potable water systems (DCPC, 2017). Treatment requirements for non-potable rainwater collection systems are described in this summary.
Onsite non-potable water reuse applications approved for use in District of Columbia
Washington, D.C. DOEE (2020) defines the following onsite non-potable water reuse applications for harvested rainwater:
- Landscape irrigation
- Exterior washing (e.g., car washes, building facades, sidewalks, street sweepers and fire trucks)
- Flushing toilets and urinals
- Fire suppression (e.g., sprinkler systems)
- Supply for cooling towers, evaporative coolers, fluid coolers and chillers
- Replenishment of water features and water fountains
- Distribution of green wall or living wall systems
- Laundry
Additional onsite non-potable water reuse applications for treated rainwater from rainwater collection and distribution systems are not specified.
Water reuse treatment category/type
Washington, D.C. does not assign harvested rainwater used for onsite non-potable water reuse to a category or class. Non-potable water for each end use application must meet minimum water quality requirements as established for the intended application (DCPC, 2017). In the cases where non-potable water from multiple sources is combined in a single system, the system must comply with the most stringent source water requirements (DCPC, 2017).
Specific treatment requirements are provided for non-potable rainwater collection and distribution systems. All treatment devices must allow access for inspection, maintenance and cleanout (DCPC, 2017). A method for indicating servicing or replacement must also be established (DCPC, 2017).
Washington, D.C. requires non-potable water to be disinfected as necessary to meet water quality requirements for the intended onsite water reuse application. Disinfection methods include the use of free chlorine, chloramines, peracetic acid, ozone, ultraviolet radiation, advanced oxidation and pasteurization at 60°C. The doses for each method depend on the log-reduction target of the target microorganisms. When chlorine is used for treatment, water must be tested for residual chlorine in accordance with ASTM D1253 and not exceed levels allowed for intended end use (DCPC, 2017).
Additional context and definitions
Washington, D.C. allows rainwater to be collected only from above-ground impervious roofing surfaces for onsite non-potable water reuse applications as long as the collected water is treated per the specifications in the table (DOEE, 2020). Collection surface, roof gutters and downspouts must be constructed from approved materials to meet the rainwater quality for the desired end use (DCPC, 2017). Leaf screens and gutter guards are the minimum criteria for prefiltration of rainwater harvesting systems (DOEE, 2020). Downspouts and leaders must be connected to a debris excluder or equivalent device that is designed to remove leaves, sticks, pine needles and similar debris to prevent such from entering the storage tank (DCPC, 2017). Collected rainwater must be further filtered as required for the intended end use (DCPC, 2017). At the beginning of rainfall events, enough water must be diverted away to wash away debris and other contaminants from entering the storage tank (DCPC, 2017). The roof gutters and downspouts must have a continuous slope greater or equal to an eighth of an inch per foot towards the collection inlets and not permit the pooling of water at any point along the slope (DCPC, 2017). Cleanouts must be provided in the rainwater collection system to allow access to all filters, flushes, pipes and downspouts (DCPC, 2017).
Washington, D.C. requires specific design elements when implementing rainwater collection and distribution practices. All components of the rainwater storage tank must be constructed of approved durable, nonabsorbent and corrosion-resistant materials which are compatible with any disinfection systems (DCPC, 2017). Non-potable water storage tanks can either be located above or below-ground. Above-ground storage tanks must be constructed using opaque, UV-resistant materials (e.g., heavily tinted plastic, fiberglass, lined metal, concrete, wood or painted) to prevent algae growth (DCPC, 2017). Below ground storage tanks are prohibited from being located under any soil pipe, waste pipe or other potential source of contamination (DCPC, 2017). All non-potable water storage tanks must be made identifiable by being painted with the color purple and including signage with the words “CAUTION: NONPOTABLE WATER – DO NOT DRINK.” (DCPC, 2017).
Onsite non-potable water reuse specifications
Summary of Washington, D.C’s Onsite Non-potable Water Reuse Specifications
| Recycled Water Class/Category | Source Water Type | Water Quality Parameter | Specification | Sampling/Monitoring Requirements (Frequency of monitoring; site/ location of sample; quantification methods)a |
|---|---|---|---|---|
|
Onsite non-potable water reuse (e.g., landscape irrigation, toilet flushing)b |
Rainwater (roof runoff not subject to frequent public access) |
Enteric bacteria |
3.5 log reduction (irrigation and indoor use) |
Not specified |
Source = DOEE (2020)
a Information about sampling and monitoring requirements such as frequency, site and quantification methods not specifically listed in the table was not explicitly specified in the State-specific regulations.
b Water used in cooling towers does not have target log reductions.
Upcoming state law or policy
No upcoming onsite non-potable water reuse regulations related to rainwater were found for Washington, D.C.
References:
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
DC Plumbing Code (DCPC). 2017.
Department of Energy and Environment (DOEE). 2020. Stormwater Management Guidebook.
Water and Sanitation, Water Quality and Pollution, 21 DCMR § 5.
Please contact us at waterreuse@epa.gov if the information on this page needs updating or if this state is updating or planning to update its laws and policies and we have not included that information on the news page.