California Code, Water Code - WAT § 13523

(a) Each regional board, after consulting with and receiving the recommendations of the State Department of Public Health and any party who has requested in writing to be consulted, and after any necessary hearing, shall, if in the judgment of the board, it is necessary to protect the public health, safety, or welfare, prescribe water recycling requirements for water that is used or proposed to be used as recycled water.

(b) The requirements may be placed upon the person recycling water, the user, or both.  The requirements shall be established in conformance with the uniform statewide recycling criteria established pursuant to Section 13521.  The regional board may require the submission of a preconstruction report for the purpose of determining compliance with the uniform statewide recycling criteria.  The requirements for a use of recycled water not addressed by the uniform statewide recycling criteria shall be considered on a case-by-case basis.