California Green Building Code (CALGreen) – Graywater irrigation system

These actions are intended to end the use of potable water for irrigation of landscapes. They place a strong emphasis on maintaining the drinkable resource only for food production and consumption by people, animals, and plants.

CALGreen Code Section A5.304.8: Graywater irrigation system.

Install a graywater collection system for onsite subsurface irrigation using graywater collected from bathtubs, showers, bathroom wash basins and laundry water. See California Plumbing Code.


The intent of these measures is to eliminate the use of potable water for landscape irrigation. They emphasize preserving the potable resource exclusively for human and wildlife consumption and for growing food. Furthermore, these provisions implement, interpret and make specific the provisions of Health and Safety Code Section 18941.8, which authorizes the California Building Standards Commission to promulgate building standards for graywater use in specified nonresidential applications. The California Plumbing Code includes provisions for the installation of graywater systems. There may be local prohibitions or requirements for the use of graywater.

Compliance Method:

Provide a graywater irrigation system complying with the California Plumbing Code, as acceptable to the local jurisdiction. Detail in construction documents a graywater system piping plan and specifications for system components.


Plan intake: The plan reviewer should confirm in the construction documents a graywater system piping plan and component specifications. The reviewer should make sure that the graywater system for irrigation meets applicable local, regional and state standards.

On-site enforcement: The inspector should verify that the system is installed as shown in the drawings, using the specified components.

(Excerpted from ‘Guide to the 2022 California Green Building Standards Code Nonresidential’ – Appendix A5)

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