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Residential Clothes Washer Gray Water System

In California, gray water can be used for landscape irrigation, which helps conserve our drinking supply while reducing your water bill.

A gray water system that collects the used water from a residential clothes washing machine must be installed in accordance with regulations of the California Plumbing Code, Section 1503.0 - Gray Water Systems (chapter for Alternate Water Systems for Nonpotable Applications).

Do not allow gray water to:

  • Have contact with humans or pets;
  • Irrigate garden vegetables intended for human consumption; 
  • Include wash water used for washing diapers or any materials that may contain hazardous chemicals, such as rags used with cleaning products. An approved three-way diverter valve is required to divert water to the sanitary sewer when the washer is for such items.

The system design should distribute the water into a subsurface or subsoil dispersion field or mulch basin.

Soaps, shampoos, detergent and cleansers that are used in Gray Water systems must be biodegradable and safe for gray water use. See this guide for Gray Water-Compatible Cleaning Products. 

When Permits are Required

 If there are no modifications to the plumbing or electrical systems, a single residential clothes washer gray water system does NOT require a building permit. In all other cases, a gray water system requires a plan review and a building permit.

Please check with the Building Division to see if your gray water project requires a permit. Contact us via email at: InfoInspector@sanjoseca.gov

Resources & Rebates

To learn more about gray water and possible rebates for a gray water system, visit:

See also the Environmental Services Department's Water Conservation page to learn more about what you can do to conserve water.