California Recycled Water Regulations & Reuse Requirements

California regulates recycled water through a combination of Water Code requirements, State Water Resources Control Board policy, Regional Water Quality Control Board permits, Division of Drinking Water public-health review, and Title 22 Water Recycling Criteria.

For operators, the important principle is that recycled water must be produced, distributed, and used according to the treatment level, permit conditions, approved engineering report, and public-health protections that apply to the specific project.

California Water Recycling Criteria

The Uniform Statewide Recycling Criteria are contained in Title 22, Division 4, Chapter 3 of the California Code of Regulations.

These criteria establish public-health requirements for recycled-water uses and connect the required treatment level with the intended use.

Recycled Water Is Not One Uniform Product

The term recycled water can describe water treated to different levels for different approved uses.

An operator should not assume that water acceptable for one recycled-water application is automatically acceptable for every other application.

Treatment Must Match the Intended Use

California recycled-water requirements are based on the intended end use and the level of public exposure.

Higher-exposure applications generally require more protective treatment and operational controls.

Operators must follow the treatment and monitoring requirements established for the specific permitted project.

Regional Water Board Permits

Recycled-water projects generally require permit coverage from the appropriate Regional Water Quality Control Board.

The Regional Water Board coordinates with the State Water Board Division of Drinking Water to ensure the project complies with applicable water-quality and public-health requirements.

General and Individual Permit Coverage

Depending on the project, recycled-water use can be regulated through an applicable general order or an individual permit.

Operators should identify the actual order governing their project rather than assume all recycled-water facilities operate under one statewide permit.

Title 22 Engineering Report

A recycled-water project must demonstrate compliance with Title 22 requirements, including preparation of an engineering report describing the project.

The engineering report can address:

• source wastewater;
• treatment processes;
• recycled-water quality;
• intended uses;
• distribution system;
• use areas;
• monitoring;
• cross-connection control;
• operational safeguards;
• other public-health protections.

The Engineering Report Is an Operating Reference

The engineering report is not merely a design document that becomes irrelevant after construction.

Operators should understand the approved treatment and operational assumptions because facility changes or new end uses can require regulatory review.

Nonpotable Recycled Water Uses

Approved recycled-water uses can include applications such as:

• landscape irrigation;
• agricultural irrigation;
• industrial uses;
• toilet and urinal flushing in approved systems;
• construction uses;
• other permitted nonpotable applications.

The required treatment and control measures depend on the specific use.

Disinfected Tertiary Recycled Water

Disinfected tertiary recycled water is a highly treated category used for applications with greater potential for public contact.

Operators should understand that tertiary treatment requirements involve treatment performance and disinfection requirements that must be maintained consistently, not only demonstrated during startup.

Disinfected Secondary Recycled Water

Some recycled-water applications can use disinfected secondary recycled water when allowed by Title 22 and the project permit.

The operator should rely on the approved project requirements rather than assume disinfected secondary water is appropriate for every irrigation or industrial use.

Undisinfected Secondary Recycled Water

Lower-treatment recycled water is limited to uses where the potential for public exposure is controlled and the applicable criteria allow it.

The required separation, access control, signage, and use restrictions become especially important where treatment is less protective.

Monitoring

Recycled-water operations can require monitoring of treatment performance and water quality.

Depending on the facility and permit, monitoring can include:

• flow;
• turbidity;
• disinfectant performance;
• microbiological indicators;
• other permit-specific parameters.

Continuous Process Control

Where a treatment requirement depends on continuous process performance, an operator must respond promptly to alarms, equipment failures, or out-of-specification conditions.

Producing recycled water outside approved treatment conditions can require diversion, shutdown, or other corrective action specified in the permit or engineering report.

Off-Specification Recycled Water

Water that does not meet the required recycled-water quality should not be distributed or used as though it were compliant product water.

Operators should follow facility procedures for:

• diversion;
• retreatment;
• storage;
• disposal;
• notification;
• documentation.

Cross-Connection Protection

Recycled-water systems must be protected against cross-connections with potable water systems.

California's current Cross-Connection Control Policy Handbook provides important backflow-protection requirements relevant to recycled-water systems.

Operators should treat any suspected potable-recycled cross-connection as a serious public-health issue.

Dual-Plumbed Systems

Dual-plumbed facilities contain separate potable and recycled-water piping systems.

These systems require special controls because an incorrect connection can introduce recycled water into the potable plumbing system.

Important protections can include:

• approved design;
• cross-connection testing or inspection;
• proper identification;
• controlled modifications;
• approved backup or supplemental arrangements.

Purple Pipe Identification

California uses purple identification for recycled-water distribution piping.

The purpose is to distinguish nonpotable recycled-water facilities from potable-water systems and reduce the risk of accidental cross-connections or misuse.

Identification Does Not Replace Control

Purple pipe is an important identification tool, but color alone does not make a system safe.

Operators must also maintain:

• accurate maps;
• valve identification;
• cross-connection protection;
• approved use areas;
• proper signage;
• operational controls.

Signage

Recycled-water use areas can require signs or other identification to inform workers and the public that recycled water is being used and is not intended for drinking.

Signage should be maintained in readable condition and located according to the applicable project requirements.

Preventing Public Exposure

Recycled-water use must be managed to prevent exposure conditions that are inconsistent with the approved use.

Depending on the project, operational controls can address:

• spray drift;
• ponding;
• runoff;
• overspray;
• public access;
• contact with potable-water facilities.

Storage and Distribution

Recycled-water storage and distribution facilities must be operated to preserve required water quality and prevent unauthorized or incorrect use.

Operators should monitor conditions such as:

• storage level;
• turnover;
• disinfectant conditions where applicable;
• valve position;
• system pressure;
• distribution integrity.

Backflow and Pressure

Pressure differences can create backflow risk between potable and nonpotable systems.

Operators should understand both backsiphonage and backpressure and maintain the approved protection required by the cross-connection control program.

Recycled Water Policy

The State Water Board's Recycled Water Policy supports the safe use of recycled water while protecting public health and water quality.

The policy provides direction for Regional Water Boards and recycled-water project proponents when permits are issued.

Statewide Recycled-Water Reporting

The Recycled Water Policy includes statewide annual reporting requirements for recycled-water production and use and for wastewater treatment and discharge volumes.

Accurate operational flow data therefore supports both plant control and statewide regulatory reporting.

Salt and Nutrient Management

Recycled-water projects can affect groundwater salt and nutrient conditions.

Regional Water Board permitting can therefore consider salt and nutrient management, groundwater protection, and antidegradation requirements.

Wastewater Change Petition Review

Before implementing a recycled-water project, the project must consider whether changing the location or amount of wastewater discharge could affect water rights.

The State Water Board provides a Water Code section 1211 wastewater change-petition checklist to help determine whether a petition is needed.

Indirect Potable Reuse

Indirect potable reuse projects are subject to additional requirements beyond ordinary nonpotable reuse.

Examples include groundwater recharge and surface-water augmentation projects.

Operators should not apply nonpotable recycled-water criteria as though they fully define potable-reuse requirements.

Direct Potable Reuse

California adopted direct potable reuse regulations effective October 1, 2024.

Direct potable reuse uses advanced treatment and a separate regulatory framework designed for potable applications.

It should not be confused with conventional nonpotable recycled-water use.

Onsite Treatment and Reuse of Nonpotable Water

California regulations for onsite treatment and reuse of nonpotable water became effective April 22, 2026.

These regulations establish risk-based water-quality standards for specified onsite nonpotable systems in multifamily residential, commercial, and mixed-use buildings.

Onsite Nonpotable Systems Are a Separate Framework

Operators should distinguish centralized recycled-water systems from building-scale onsite nonpotable reuse systems.

Although both involve reuse, they can have different regulatory structures, treatment requirements, and responsible entities.

Coordination With Drinking Water Systems

Recycled-water projects often require coordination with public water systems because potable and recycled-water infrastructure can exist near each other.

This is especially important for:

• cross-connection control;
• dual-plumbed facilities;
• backflow protection;
• construction review;
• incident response.

Incident Response

If recycled water enters a potable system or another prohibited connection is suspected, operators should act immediately according to the facility's approved procedures and applicable regulatory requirements.

Actions can include:

• isolating affected facilities;
• stopping recycled-water flow;
• notifying responsible personnel;
• contacting regulatory agencies;
• sampling;
• flushing and disinfection where required;
• documenting the investigation and corrective action.

Recordkeeping

Useful recycled-water records can include:

• permit and order;
• engineering report;
• monitoring data;
• treatment-process records;
• cross-connection test results;
• distribution-system maps;
• use-site inspections;
• incident records;
• maintenance records;
• annual reporting data.

Operator Responsibilities

Wastewater and recycled-water operators should understand how their process affects final recycled-water quality and approved uses.

Important responsibilities can include:

• maintaining treatment barriers;
• responding to alarms;
• verifying disinfection performance;
• monitoring product-water quality;
• diverting off-specification water;
• maintaining records;
• communicating abnormal conditions.

Common Exam Mistakes

• Assuming all recycled water can be used for the same purposes.
• Ignoring the relationship between treatment level and intended use.
• Treating the Title 22 engineering report as a one-time paperwork exercise.
• Distributing off-specification recycled water as normal product water.
• Assuming purple pipe alone prevents cross-connections.
• Ignoring signage and use-area controls.
• Confusing nonpotable recycled water with indirect or direct potable reuse.
• Ignoring Regional Water Board permit requirements.
• Failing to maintain accurate recycled-water production and use records.
• Ignoring potential water-right implications of changing wastewater discharge.

A Practical Recycled-Water Review

1. Identify the current Regional Water Board permit or order.
2. Review the approved Title 22 engineering report.
3. Confirm the recycled-water treatment category and approved end uses.
4. Maintain required treatment and disinfection performance.
5. Monitor required water-quality and process parameters.
6. Divert or otherwise control off-specification recycled water.
7. Protect potable systems from cross-connections.
8. Maintain purple-pipe identification, signage, maps, and use-site controls.
9. Maintain inspection, monitoring, and incident records.
10. Complete required reporting and coordinate with regulatory agencies when project conditions change.

What to Remember for the Exam

• California Uniform Statewide Recycling Criteria are in Title 22, Division 4, Chapter 3.
• Recycled-water treatment requirements depend on the intended use and potential public exposure.
• Regional Water Boards generally issue recycled-water permits and coordinate with the Division of Drinking Water.
• A Title 22 engineering report describes treatment, intended uses, monitoring, distribution, and public-health safeguards.
• Recycled water acceptable for one use is not automatically acceptable for every other use.
• Off-specification recycled water must be managed according to the approved permit and facility procedures.
• Cross-connection protection is essential where potable and recycled-water systems coexist.
• Dual-plumbed systems require special controls to prevent potable-recycled cross-connections.
• Purple pipe identifies recycled-water piping but does not replace backflow protection, maps, signage, or operational controls.
• The Recycled Water Policy includes statewide annual reporting for recycled-water production and use and wastewater treatment and discharge volumes.
• Recycled-water projects can require evaluation of salt, nutrient, groundwater, and water-right impacts.
• Indirect potable reuse and direct potable reuse have additional regulatory requirements beyond ordinary nonpotable reuse.
• California direct potable reuse regulations became effective October 1, 2024.
• California onsite nonpotable treatment and reuse regulations became effective April 22, 2026.
• Operators must maintain treatment barriers, monitoring, records, cross-connection protection, and approved end-use controls.