Might not be in County codes since its a State code.
California law (Health & Safety Code Sections 19210-19217) requires:
• Any new or replacement water heater sold in California on or after July 1, 1991 be braced,
anchored or strapped when installed to resist falling or horizontal displacement due to
earthquake forces.
• The seller of any real property containing a water heater to certify in writing to the purchaser
that water heater bracing requirements have been met.