Wat. Code, § 112

(a) The efficiency of a reverse osmosis water treatment device means the percentage of water which passes through the water treatment device that is available for subsequent domestic use and which is not discharged directly from the device to the waste disposal system of the residence where the device is used.

(b) Notwithstanding any other provision of law, after January 1, 1991, no reverse osmosis water treatment device shall be sold, installed, or rented, for residential use, including any general domestic purposes such as drinking, cleaning, washing, or sanitation, unless the device is equipped with an automatic waste shutoff device or, through other equipment design specifications, achieves or exceeds equal or greater water savings than would occur with an automatic shutoff device.

(c) Effective January 1, 1993, any reverse osmosis water treatment device sold, installed, rented, or under service contract prior to January 1, 1991, for residential use shall be retrofit with an automatic waste shutoff device, or, through other equipment design specifications, achieve or exceed equal or greater water savings than would occur with an automatic shutoff device.