Chapter 15 — ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS
1503.1 General — 2025 California Plumbing Code
California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-09-25 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Plumbing Code (Title 24, Part 5) § 1503.1 · Effective January 1, 2026 · Official source: Building Standards Commission
The provisions of this section shall apply to the construction, alteration, and repair of gray water systems. A city, county, or city and county or other local government may adopt, after a public hearing and enactment of an ordinance or resolution, building standards that are more restrictive than the gray water building standards adopted in this code. For addi- tional information, see Health and Safety Code Section 18941.7.
(A) All gray water systems shall be designed with a diverter valve to allow the user to direct the flow to the building sewer and either the irrigation field or disposal field, whichever is used. The means of changing the direction flow of the gray water shall be clearly labeled and readily accessible to the user.
(B) Water used to wash diapers or similarly soiled or infec- tious garments or other prohibited contents shall be diverted by the user to the building sewer.
(C) Gray water shall not be used in spray irrigation, allowed to pond or runoff and shall not be discharged directly into or reach any storm sewer system or any surface body of water.
(D) Human contact with gray water or the soil irrigated by gray water shall be minimized and avoided, except as required to maintain the gray water system. The dis- charge point of any gray water subsoil irrigation or sub- surface irrigation field shall be covered by at least two (2) inches (51 mm) of mulch, rock, or soil, or a solid shield to minimize the possibility of human contact.
(E) Gray water may be released above the ground surface provided at least two (2) inches (51 mm) of mulch, rock, or soil, or a solid shield covers the release point. Other methods which provide equivalent separation are also acceptable.
(F) Gray water shall not contain hazardous chemicals derived from activities such as cleaning car parts, wash- ing greasy or oily rags, or disposing of waste solutions.
(1) [HCD 1] The prohibition in Subsection (F) includes, but is not limited to, home photo labs or other similar hobbyist or home occupational activities.
(2) [BSC-CG] Photo labs or similar activities.
(G) Exemption from construction permit requirements of this code shall not be deemed to grant authorization for any
gray water system to be installed in a manner that vio- lates other provisions of this code or any other laws or ordinances of the Enforcing Agency.
(H) An operation and maintenance manual shall be provided to the owner. Directions shall indicate that the manual is to remain with the building throughout the life of the system and upon change of ownership or occupancy.
(I) A gray water system shall not be connected to any potable water system without an air gap, reduced-pressure prin- ciple backflow preventer, or other physical device which prevents backflow and shall not cause ponding or runoff of gray water.
1503.1.1 Clothes Washer System. [HCD 1] A clothes washer system in compliance with all of the fol- lowing is exempt from the construction permit specified in Section 1.8.4.1 and may be installed or altered with- out a construction permit:
(1) If required, notification has been provided to the enforcing agency regarding the proposed location and installation of a gray water irrigation or dis- posal system.
(2) The design shall allow the user to direct the flow to the irrigation or disposal field or the building sewer. The direction control of the gray water shall be clearly labeled and readily accessible to the user.
(3) The installation, change, alteration, or repair of the system does not include a potable water connection or a pump and does not affect other building, plumb- ing, electrical, or mechanical components including structural features, egress, fire-life safety, sanitation, potable water supply piping, or accessibility.
Note: The pump in a clothes washer shall not be considered part of the gray water system.
(4) The gray water shall be contained on the site where it is generated.
(5) Gray water shall be directed to and contained within an irrigation or disposal field.
(6) Ponding or runoff is prohibited and shall be consid- ered a nuisance.
(7) Gray water may be released above the ground sur- face provided at least two (2) inches (51 mm) of mulch, rock, or soil, or a solid shield covers the release point. Other methods which provide equiva- lent separation are also acceptable.
(8) Gray water systems shall be designed to minimize contact with humans and domestic pets.
(9) Water used to wash diapers or similarly soiled or infectious garments shall not be used and shall be diverted to the building sewer.
(10)Gray water shall not contain hazardous chemicals derived from activities such as cleaning car parts, washing greasy or oily rags, or disposing of waste solutions from home photo labs or similar hobbyist or home occupational activities.
312 2025 CALIFORNIA PLUMBING CODE
ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS
(11) Exemption from construction permit requirements of this code shall not be deemed to grant authorization for any gray water system to be installed in a man- ner that violates other provisions of this code or any other laws or ordinances of the enforcing agency.
(12)An operation and maintenance manual shall be pro- vided to the owner. Directions shall indicate that the manual is to remain with the building throughout the life of the system and upon change of ownership or
occupancy.
(13)Gray water discharge from a clothes washer system through a standpipe shall be properly trapped in accordance with Section 1005.0.
1503.1.2 Simple System. Simple systems exceed a clothes washer system and shall comply with the follow- ing:
(1) The discharge capacity of a gray water system shall be determined by Section 1503.8. Simple systems have a discharge capacity of 250 gallons (947 L) per day or less.
(2) Simple systems shall require a construction permit, unless exempted from a construction permit by the Enforcing Agency. The Enforcing Agency shall con- sult with the water purveyor for any public water sys- tem (as defined in Health and Safety Code Section 116275) providing drinking water to the dwelling or non-residential structure before allowing an exemp- tion from a construction permit.
(3) The design of simple systems shall meet generally accepted gray water system design criteria. 1503.1.3 Complex System. Any gray water system that is not a clothes washer system or simple system shall comply with the following:
(1) The discharge capacity of a gray water system shall be determined by Section 1503.8. Complex systems have a discharge capacity over 250 gallons (947 L) per day.
(2) Complex systems shall require a construction permit, unless exempted from a construction permit by the Enforcing Agency. The Enforcing Agency shall con- sult with the water purveyor for any public water sys- tem (as defined in Health and Safety Code, Section 116275) providing drinking water to the dwelling or non-residential structure before allowing an exemp- tion from a construction permit.
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