Summary of California’s Water Reuse Guideline or Regulation for Onsite Non-potable Water Reuse and Landscaping
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 Onsite Collected Waters.
- Technical basis
- Background on NSF/ANSI Standard 350
- Types of onsite non-potable reuse approved for use in California
- 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 California, onsite non-potable water reuse The use of treated onsite collected waters for non-potable purposes at the single-building or district scale. This reuse application excludes the use of recycled water from a centralized treatment and distribution system for landscape irrigation or commercial uses. applications include toilet and urinal flushing, and water reuse for landscapingThe use of recycled water on land to assist in the irrigation of vegetation in residential and non-residential areas. Includes impoundments to store water for irrigation , ornamental vegetation, parks, school yards, sporting facilities (including golf courses), private gardens, roadsides and greenbelts, and cemeteries. Excludes irrigation of areas used for agriculture, commercial reuse applications, or any centralized non-potable reuse. applications for irrigation and ornamental fountains, among others. The source of water onsite collected waters Water sources generated within or surrounding a building, residence, or district. Other terms referring to this source of water include onsite collected stormwater or rainwater, greywater, blackwater, air conditioning condensate, and foundation water. is specified by the state as graywater. 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.
Check out California's other landscaping summary!
State requirements for water quality and treatment are often associated with the source water. California has a landscaping summary page where the source water is treated municipal wastewater.
Check out California's other onsite non-potable water reuse summary!
State requirements for water quality and treatment are often associated with the source water. California has an onsite non-potable water reuse summary page where the source water is rainwater collected onsite.
Technical basis
California approves the onsite non-potable reuse of treated graywater for toilet and urinal flushing and landscape irrigation. 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 state water quality standards. The minimum water quality requirements for onsite non-potable graywater systems are determined by the local public health authority. Local jurisdictions are not mandated to regulate onsite treated non-potable water systems, and in the absence of local treatment requirements for onsite graywater, the NSF/ANSI Standard 3501 are applied (Cal. Code Regs. tit. 24, § 5). The local authority requirements may be more stringent than the NSF/ANSI requirements.
Background on NSF/ANSI Standard 350
The National Sanitation Foundation/American National Standards Institute (NSF/ANSI) was originally adopted in 2011 and includes requirements for testing onsite residential and commercial water reuse treatment systems. NSF/ANSI 350 includes requirements for two categories of facilities: residential (up to 1,500 gallons per day), and commercial (systems exceeding 1,500 gallons per day); and four different types of influent: (1) combined black and gray water; (2) gray water only; (3) bathing water only; and (4) laundry water only. The standard covers general non-potable reuse applications, including surface and subsurface irrigation, and toilet and urinal flushing. There are two categories of effluent criteria that vary slightly: Class R for single family residential, and Class C for multi-family residential and commercial. These effluent quality criteria were developed using the currently existing guidelines, codes and regulations, with the goal of meeting the majority of existing codes (although the guidelines do not meet all state codes). Class R includes E. coli water quality requirements not to exceed 14 MPN/100 mL geometric mean and 240 MPN/100 mL single sample maximum, and Class C includes E. coli water quality requirements not to exceed 2.2 MPN/100 mL geometric mean and 200 MPN/100 mL single sample maximum.
Types of onsite non-potable reuse approved for use in California
Cal. Code Regs. tit. 24, § 5 defines the following approved onsite non-potable reuse applications for the use of graywater treated by onsite non-potable graywater treatment systems:
- Toilet and urinal flushing,
- Above and below ground irrigation,
- Trap primers for floor drains and floor sinks.
Water reuse category/type
California does not assign treated graywater used for onsite non-potable reuse to a category or class.
Additional context and definitions
The respective treatment requirements for graywater are summarized for onsite non-potable reuse applications:
- Graywater used for urinal and toilet flushing must be disinfected via chlorination, UV, ozone, or other methods as approved by the local health authority.
- "Graywater" means untreated wastewater that has not been contaminated by any toilet discharge or infection, contaminated or unhealthy bodily wastes. Examples of graywater include wastewater from bathtubs, showers, clothes washing machines and laundry tubs, but does not include wastewater from kitchen sinks or dishwashers.
- “Graywater” as defined above has the same meaning as “gray water”, “grey water” and “greywater” (Cal. Code Regs. tit. 24, § 5)
Onsite non-potable reuse specifications
Summary of California's Non-potable 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) |
|---|---|---|---|---|
|
Onsite treated non-potable graywater systems (toilet and urinal flushing, above and below ground irrigation, trap primers) |
Graywater |
The minimum water quality for onsite treated non-potable graywater systems shall meet the applicable water quality requirements for the intended applications as determined by the public health authority having jurisdiction. In the absence of local water quality requirements for onsite treated non-potable graywater, the requirements of ANSI/NSF 350 shall apply. |
||
Sources = Cal. Code Regs. tit. 24, § 5
Upcoming state law or policy
The California legislature has specified a December 1, 2022 deadline for the State Board adoption of risk-based water quality standards for onsite treatment and reuse of non-potable water systems, with a December 1, 2023 deadline for the Department of Housing and Community Development to adopt corresponding building standards. California’s fit-for-purpose specifications may change based on the adoption of the risk-based quality standards, except for untreated graywater systems used exclusively for subsurface irrigation (regulated by Chapter 15 of Cal. Code Regs. tit. 24, § 5) and untreated rainwater systems used exclusively for surface, subsurface or drip irrigation (regulated by Chapter 16 of Cal. Code Regs. tit. 24, § 5).
References:
2019 California Plumbing Code, Cal. Code Regs. tit. 24, § 5.
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
Onsite Residential and Commercial Water Reuse Treatment Systems, NSF/ANSI Standard 350.
Onsite Treated Nonpotable Water Systems, Cal. S.B. 966, Chapter 890, Cal. Stat. (2018).
Please contact us at [email protected] 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.