Test the water heater's relief valve
Annual · typically April
Why it matters
On top or high on the side of your tank is a brass valve with a flip lever — the temperature-pressure relief (TPR) valve. Its whole job is to open before tank pressure becomes dangerous. It is the single most important safety device on the appliance, and like any mechanical part sitting in hot mineral-laden water, it can seize.
Pair this with your annual tank flush — same corner of the house, same afternoon.
What skipping it costs
$250–$8,000
The temperature-pressure relief valve is the reason water heaters don't explode. If it seizes shut with sediment and the thermostat ever fails, the tank becomes a pressure vessel with no exit — the failure is rare, and it's also the one that puts tanks through roofs. The everyday version of neglect is quieter: a seized valve fails inspection at resale, or weeps unnoticed into the pan for a year.
Two ways to get it done
Do it yourself
You'll need: A bucket, Work gloves.
- Look first: the valve should have a discharge pipe running down toward the floor. If there's no pipe — just a bare valve — skip the test and call a plumber to add one; testing without it sprays scalding water.
- Put a bucket under the discharge pipe's end.
- Lift the lever partway and let it snap back. You should hear a rush and see hot water spit into the bucket. That's a pass — the valve moves.
- If nothing comes out, the valve is seized. If it won't stop dripping afterward (give it a few hours; a brief dribble is normal), the seat didn't reseal.
- Either result means a valve replacement — a $20–$30 part, and a legitimately easy plumber visit. Don't force a stuck lever harder; seized is seized.
Fair warning: on an old valve that's never been tested, the test itself sometimes causes the drip. That's not the test breaking the valve — that's the valve telling you it was already at the end.
Hire it out
$150–$275National fair range — local labor moves this number.
A plumber visit to test and replace the TPR valve runs $150–$275 including the part — reasonable, given it involves partially draining the tank. Have them verify the discharge pipe while they're there: full-size, no threads on the outlet end, terminating near the floor.
Two upsells live in this corner. The expansion tank is the honest one — on a closed system (backflow preventer or check valve at the meter), thermal expansion has nowhere to go and an expansion tank is genuinely correct; make them show you the check valve. The dishonest one is converting a $20 valve replacement into a same-day tank replacement on urgency alone. A dripping TPR valve is a symptom to diagnose, not a countdown.
Ask the tech
- Is the discharge pipe the right size and routed down to within 6 inches of the floor?
- If the valve needs replacing, is that included in this price or on top?
- Do I actually need an expansion tank — is my system closed? Show me the check valve or PRV that makes it so.
Red flags you're being upsold
- 'You need a whole new water heater' because the valve dripped once during a test — the valve is a $20 part.
- An expansion tank hard-sell without demonstrating you have a closed system. (On a genuinely closed system it's legitimate — the difference is whether they show you why.)
- Testing the valve, watching it stick, and quoting an emergency replacement 'before it bursts tonight.' Urgency is the tell.
Second opinion time: Any replacement quote over $2,000 that started as a valve question.
The call
DIY the test if the valve has a discharge pipe and you can reach it; it's a lever and a bucket. Anything the test reveals — that's the plumber.