What California law and state agencies say about water heaters
California Health and Safety Code section 19211 requires all new, replacement and existing residential water heaters to be braced, anchored or strapped to resist falling or shifting in an earthquake, and a seller of property with a water heater must certify to the buyer in writing that this has been done. The California Seismic Safety Commission's Homeowner's Guide to Earthquake Safety tells homeowners to look for two sets of straps wrapped around the heater and bolted to the wall studs, suggests having a licensed plumber replace rigid water heater pipes with flexible ones, and says a tankless unit should be securely attached to the wall, with its pipes installed according to the manufacturer's instructions.
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The California Energy Commission's residential compliance manual reports that most manufacturers recommend draining a tank water heater every six months to once a year to clear sediment, and inspecting the burner, venting and temperature and pressure relief valve on the same schedule. For tankless units, it names flushing scale from the heat exchanger and cleaning the inlet filter screen as the main upkeep, recommended every two years where water is hard. It notes that softened water corrodes a tank's anode rod much faster, and that a heat pump water heater's air filter needs checking three to four times a year.
California's Energy Code requires a newly installed tankless water heater to have isolation valves on its cold water supply and hot water outlet, unless the unit has built-in service drain ports, and the Energy Commission says the valves help with flushing and prolong the heater's life. The Contractors State License Board lists C‑36 Plumbing and C‑20 HVAC as the license classifications for installing and repairing heat pump water heaters.

