Cal. Health & Safety Code § 18031.7

(a) Nothing in this part shall prohibit the replacement of water heaters in manufactured homes or mobilehomes with fuel-gas-burning water heaters not specifically listed for use in a manufactured home or mobilehome or from having hot water supplied from an approved source within the manufactured home or mobilehome, or in the garage, in accordance with this part or Part 2.1 (commencing with Section 18200).
(b) Nothing in this part shall prohibit the replacement of appliances for comfort heating in manufactured homes, mobilehomes, or multifamily manufactured homes with fuel-gas appliances for comfort heating not specifically listed for use in a manufactured home or mobilehome within the manufactured home, mobilehome, or multifamily manufactured home in accordance with this part, Part 2.1 (commencing with Section 18200), or Part 2.3 (commencing with Section 18860).
(c) Replacement fuel-gas-burning water heaters shall be listed for residential use and installed within the specifications of that listing to include tiedown or bracing to prevent overturning.
(d) Replacement fuel-gas-burning water heaters installed in accordance with subdivision (c) shall bear a label permanently affixed in a visible location adjacent to the fuel gas inlet which reads, as applicable:
WARNING This appliance is approved only for use with natural gas (NG).
OR
WARNING This appliance is approved only for use with liquified petroleum gas (LPG).
Lettering on the label shall be black on a red background and not less than 1/4 inch in height except for the word “WARNING” which shall be not less than 1/2 inch in height.
(e)
1. (1) All fuel-gas-burning water heater appliances in new manufactured homes or new multifamily manufactured homes installed in the state shall be seismically braced, anchored, or strapped pursuant to paragraph (3) and shall be completed before or at the time of installation of the homes.
2. (2) Any replacement fuel-gas-burning water heater appliances installed in existing mobilehomes, existing manufactured homes, or existing multifamily manufactured homes that are offered for sale, rent, or lease shall be seismically braced, anchored, or strapped pursuant to paragraph (3).
3. (3) On or before July 1, 2009, the department shall promulgate rules and regulations that include standards for water heater seismic bracing, anchoring, or strapping. These standards shall be substantially in accordance with either the guidelines developed pursuant to Section 19215 or the California Plumbing Code (Part 5 of Title 24 of the California Code of Regulations), and shall be applicable statewide.
4. (4) The dealer, or manufacturer acting as a dealer, responsible, as part of the purchase contract, for both the sale and installation of any home subject to this subdivision shall ensure all water heaters are seismically braced, anchored, or strapped in compliance with this subdivision prior to completion of installation.
5. (5) In the event of a sale of a home, pursuant to either paragraph (1) of subdivision (e) of Section 18035 or Section 18035.26, the homeowner or contractor responsible for the installation of the home shall ensure all fuel-gas-burning water heater appliances are seismically braced, anchored, or strapped consistent with the requirements of paragraph (3). This requirement shall be satisfied when the homeowner or responsible contractor signs a declaration stating each fuel-gas-burning water heater is secured as required by this section on the date the declaration is signed.
(f) All used mobilehomes, used manufactured homes, and used multifamily manufactured homes that are sold shall, on or before the date of transfer of title, have the fuel-gas-burning water heater appliance or appliances seismically braced, anchored, or strapped consistent with the requirements of paragraph (3) of subdivision (e). This requirement shall be satisfied if, within 45 days prior to the transfer of title, the transferor signs a declaration stating that each water heater appliance in the used mobilehome, used manufactured home, or used multifamily manufactured home is secured pursuant to paragraph (3) of subdivision (e) on the date the declaration is signed.
(g) For sales of manufactured homes or mobilehomes installed on real property pursuant to subdivision (a) of Section 18551, as to real estate agents licensed pursuant to Division 4 (commencing with Section 10000) of the Business and Professions Code, the real estate licensee duty provisions of Section 8897.5 of the Government Code shall apply to this section.