Summary of California's Water Reuse Guideline or Regulation for Centralized Non-potable 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 Treated Municipal Wastewater.
- Technical basis
- Applications of centralized non-potable reuse approved for use in California
- Water reuse category/type
- Additional context and definitions
- Centralized 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, centralized non-potable reuse The use of recycled water for centralized non-potable reuse where the water does not derive from the same site where it is to be reused. Can include, but is not limited to, toilet flushing, dust control, soil compaction, fire protection, commercial laundries, vehicle washing, street cleaning, snowmaking, and other similar uses. Excludes on-site non-potable water reuse and the use of recycled water for agriculture or landscaping. applications include toilet and urinal flushing, decorative fountains and firefighting among others. The source of water treated municipal wastewater Treated wastewater effluent discharged from a centralized wastewater treatment plant of any size. Other terms referring to this source of water include domestic wastewater, treated wastewater effluent, reclaimed water, and treated sewage. is specified by the state as domestic wastewater. 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
California allows the use of recycled water for centralized reuse applications including, but not limited to, toilet and urinal flushing, decorative fountains, commercial laundries and car washes, firefighting, street cleaning and dust control (Cal. Code Regs. tit. 22). 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 classes of recycled water treatment differ by the level of pathogen control and filtration requirements. Disinfected secondary-23 recycled water requires a 7-day median concentration of total coliform bacteria of ≤23 MPN/100 mL and disinfected tertiary recycled water requires a 7-day median concentration of total coliform bacteria of ≤2.2 MPN/100 mL. Disinfected tertiary recycled water has an additional turbidity requirement of ≤2 NTU in a 24-hour period in the filter effluent (if conventional filtration is used) or 0.2 NTU more than 5% of the time within a 24-hour period (if microfiltration, ultrafiltration, nanofiltration, or reverse osmosis membrane is used). The technical basis for the removal of pathogens is not explicitly specified.
Applications of centralized non-potable reuse approved for use in California
Cal. Code Regs. tit. 22 defines the following allowed centralized non-potable reuse applications:
- Toilet and urinal flushing (Disinfected tertiary)
- Decorative fountains (Disinfected tertiary)
- Commercial laundries (Disinfected tertiary)
- Artificial snowmaking for commercial outdoor use (Disinfected tertiary)
- Commercial car washing, including hand washes if the recycled water is not heated and the general public is excluded from the washing process (Disinfected tertiary)
- Priming drain traps and consolidation of backfill around potable water pipelines (Disinfected tertiary)
- Firefighting
- Structural firefighting (Disinfected tertiary)
- Nonstructural firefighting (e.g., wildfires including fields and forest fires where public exposure is generally expected to be lower than structural fires) (Disinfected secondary-23)
- Commercial cooling or air conditioning
- Involves the use of a cooling tower, evaporative condenser, spraying or any mechanism that creates a mist (Disinfected tertiary)
- Does not involve the use of a cooling tower, evaporative condenser, spraying or any mechanism that creates a mist (Disinfected secondary-23)
- Soil compaction, mixing concrete and dust control (Disinfected secondary-23)
- Street cleaning (Disinfected secondary-23)
Additional types of centralized non-potable uses which are not addressed by Cal. Code Regs. tit. 22 can be proposed for case-by-case review by the State Water Board Division of Drinking Water (Cal. Water Code, § 13523).
Water reuse category/type
The various classes of recycled water treatment are defined by their respective treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized for centralized non-potable reuse applications.
- For disinfected tertiary recycled water, the treatment requirements are filtration and disinfection via chlorine disinfection or another disinfection process that achieves a 5-log inactivation or removal of plaque forming units of F-specific bacteriophage MS-2 or poliovirus (when combined with filtration).
- For disinfected secondary-23 recycled water, the treatment requirements are oxidation and disinfection and water must meet a 7-day median concentration of ≤23 MPN/100 mL of total coliform bacteria, with a single sample maximum of ≤240 MPN/100 mL.
Additional context and definitions
In California, all use areas where recycled water is used that are accessible to the public must have signs posted that include the wording “RECYCLED WATER – DO NOT DRINK” and display the international “Do Not Drink” symbol or an alternative accepted by the State Water Board (Cal. Code Regs. tit. 22). No physical connection is allowed to exist between a recycled water system and a potable water system (except as allowed under Section 7604 of Cal. Code Regs. tit. 17). The portions of the recycled water in areas accessed by the general public must not include any hose bibs and must use quick couplers that differ from those used on the potable water system. Dual plumbed systems are allowed for use in California and are defined as “a system that utilizes separate piping systems for recycled water and potable water within a facility” and the recycled water is used to either serve plumbing outlets (excluding fire protection systems) within a building or for outdoor landscape irrigation at individual residences (Cal. Code Regs. tit. 22). Only a “recycled water agency” is allowed to deliver recycled water to a dual plumbed facility.
Centralized non-potable reuse specifications
Summary of California's Centralized 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)* |
|---|---|---|---|---|
|
Disinfected tertiary (toilet and urinal flushing, decorative fountains, commercial laundries, artificial snowmaking, commercial car washing, structural firefighting, commercial cooling or air conditioning that involves mist, priming drain traps, consolidation of backfill around potable water pipelines) |
Domestic wastewater |
Turbidity (if filtered by natural undisturbed soils or a bed of filter media pursuant to Cal. Code Regs. tit. 22, § 60301.320a) |
≤2 NTU (filter effluent turbidity) ≤10 NTU (single sample maximum) Influent turbidity should not exceed 5 NTU for over 15 minutes |
Continuous monitoring |
|
Turbidity (if filtered by microfiltration, ultrafiltration, nanofiltration, or reverse osmosis membrane) |
≤0.2 NTU (more than 5% of the time within a 24-hour period) ≤0.5 NTU (single sample maximum) |
Continuous monitoring |
||
|
Total coliform |
≤2.2 MPN/100 mL (7-day median) ≤23 MPN/100 mL (does not exceed in more than one sample in 30-day period) ≤240 MPN/100 mL (single sample maximum) |
At least once daily |
||
|
CTa |
≥450 milligram-minutes/L |
Must be maintained at all times with a modal contact time of at least 90 minutes, based on peak dry weather design flow |
||
|
F-specific bacteriophage MS-2 or polio virusb,c |
5-log removal |
Must be demonstrated after filtration and disinfection |
||
|
Disinfected secondary-23 (nonstructural firefighting, commercial cooling or air conditioning that does not involve mist, soil compaction, mixing concrete, dust control, street cleaning) |
Domestic wastewater |
Total coliform |
≤23 MPN/100 mL (7-day median) ≤240 MPN/100 mL (does not exceed in more than one sample in 30-day period) |
At least once daily |
Source = Cal. Code Regs. tit. 22
* 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.
a The CT is the product of total chlorine residual and modal contact time measured at the same point (Cal. Code Regs. tit. 22). This only applies if chlorine was used for disinfection.
b This only applies if a disinfection process other than chlorination was used.
c A virus that is at least as resistant to disinfection as polio virus may be used for the purposes of the demonstration.
Upcoming state law or policy
No upcoming regulations pertaining to centralized non-potable reuse were found for California.
References:
Clean Water Act, 33 U.S.C. §§ 1251 et seq.
Water Recycling Criteria, Cal. Code Regs. tit. 22.
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.