California Code, Water Code - WAT § 537.3

(a) This article does not preclude or preempt an ordinance or regulation that regulates the approval of submeter types or the installation, maintenance, reading, billing, or testing of submeters and associated onsite plumbing if the ordinance or regulation was adopted prior to January 1, 2013.

(b) It is the intent of the Legislature to preclude the adoption, and preempt the operation, of an ordinance or regulation adopted after January 1, 2013, that regulates the types of approved submeters, their installation, maintenance, reading, billing, and testing, and associated onsite plumbing.

(c) This article does not restrict the existing authority of a water purveyor, city, county, city and county, or other local agency to adopt and implement a program to promote water conservation that includes the installation of water meters and submeters, as required pursuant to subdivision (a) of Section 537.1, if the program is at least as stringent as the requirements of this article.