Summary of California’s Water Reuse Guideline or Regulation for Rainwater Collected Onsite for 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
- 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, irrigation and ornamental fountains, among others. 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 graywater and harvested 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.
Check out how California uses rainwater collected onsite for potable water reuse!
California uses rainwater collected onsite for a variety of applications, including onsite non-potable water reuse and potable water reuse. Browse the potable water reuse summary page.
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 onsite collected waters.
Technical basis
California approves the onsite non-potable reuse of harvested rainwater for toilet and urinal flushing, clothes washing, car washing, ornamental water features and irrigation (surface, subsurface, drip and spray). 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 rainwater catchment 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, an E. coli requirement of <100 CFU/100 mL and a turbidity of <10 NTU shall be applied (Cal. Code Regs. tit. 24, § 5).
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 harvested rainwater collected by rainwater catchment systems:
- Toilet and urinal flushing,
- Clothes washing,
- Ornamental fountains and other water features,
- Cooling tower make up water,
- Car washing,
- Surface, subsurface, and drip irrigation,
- Spray irrigation.
Water reuse category/type
California does not assign treated harvested rainwater used for onsite non-potable reuse to a category or class.
Additional context and definitions
The respective treatment requirements for rainwater are summarized for onsite non-potable reuse applications:
- Rainwater catchment systems are to be equipped with a debris excluder to prevent the accumulation of leaves, needles, and other debris from entering the storage tank, and a 100-micron filter for rainwater supplied to toilet and urinals.
- Rainwater catchment systems are defined as facilities used to capture, retain, and store rainwater flowing from a rooftop or other man-made above ground collection surface for subsequent onsite reuse.
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) |
|---|---|---|---|---|
|
Rainwater catchment systemsa,b (toilet and urinal flushing, clothes washing, water features, cooling tower makeup, car washing, surface, subsurface, drip irrigation, spray irrigation) |
Harvested Rainwater |
E. coli |
<100 CFU/100 mL |
Water quality should be tested every 12 months or after system renovation or repair. |
|
Turbidity |
<10 NTU |
Sources = Cal. Code Regs. tit. 24, § 5
a There are no minimum water quality requirements for harvested rainwater used for car washing, surface/subsurface irrigation or spray irrigation where the maximum storage volume is less than 360 gallons.
b Harvested rainwater should meet the minimum water quality requirements for the intended applications as defined by the local authority having jurisdiction. In the absence of requirements, these E. coli and turbidity requirements should be used.
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 Treated Nonpotable Water Systems, Cal. S.B. 966, Chapter 890, Cal. Stat. (2018).
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.