Quick answer
- A plumbing permit is required for a water heater changeout in nearly all of CA
- Two seismic straps (upper and lower third of the tank) are required
- A T&P relief valve with a code-compliant discharge line is required
- An expansion tank is typically required on closed (check-valve/PRV) systems
- Gas units need proper venting, combustion air, and an approved gas connector
When this applies
Any water heater replacement
Whether you're going tank-to-tank, switching to tankless, or relocating the unit, the replacement needs a permit. A simple part repair (e.g., a thermostat) generally does not.
How it works
What the inspector checks
Seismic strapping, the T&P valve and its discharge routing to an approved location, expansion tank, drip/drain pan where required, venting and combustion air on gas units, the gas connector and shutoff, and correct clearances. Tankless adds gas-line sizing and venting checks.
Tank vs. tankless considerations
Tankless conversions often require a larger gas line, dedicated venting, and a condensate path — all reviewed under the permit. It's the right time to confirm the system is sized correctly for your home.
What to watch out for
An unstrapped or improperly vented unit
Missing seismic straps and bad venting are common in unpermitted swaps — both are safety hazards (earthquake and carbon-monoxide risk) and will fail inspection.
No expansion tank on a closed system
Without an expansion tank, pressure can spike on closed systems, stressing the tank and fixtures and shortening the heater's life.
Replacing a water heater? We pull the permit and install it to code.
Frequently asked questions
Can I replace my own water heater without a permit in California?
A homeowner can pull an owner-builder permit, but the work still must pass inspection and meet code. For gas units especially, most homeowners are better served by a licensed contractor who pulls the permit and takes responsibility for the result.
Does a tankless water heater need a permit too?
Yes — and often additional review for gas-line sizing, venting, and condensate, since tankless units have different requirements than a standard tank.
Is an expansion tank really required?
On a closed plumbing system (one with a pressure-reducing valve or check valve, which is common), the code generally requires thermal expansion control — usually an expansion tank. Your inspector confirms it for your setup.
Keep exploring
Reviewed by John Stevenson Plumbing, Heating & Air. Based on the California Plumbing Code requirements for water heater installation (seismic bracing, T&P relief and discharge, expansion control, venting) and our local install experience. Local amendments vary — confirm with your city or county building department. Last updated 2026-06-25.