T&P Valve Leaking: Causes, Dangers, and Fixes
T&P relief valve dripping on your Westfield, IN water heater? Why it happens, why it's urgent, and how we fix it. Call (833) 713-2101.
By Water Heater Leak Repair Contractors — Published September 30, 2026 — 12 min read
Of all the “leaks” we diagnose, the dripping temperature-and-pressure relief valve is the most common — and the most misunderstood. Homeowners see a little drip from that pipe on the side of the tank and think it's minor. Sometimes it is. Sometimes it's your water heater warning you about dangerous pressure. Knowing the difference matters.
What the T&P valve does
It's a spring-loaded safety valve set to open at 150 PSI or 210°F — conditions that can turn a water heater into a literal pressure vessel. When it opens, it dumps water down the discharge pipe to relieve pressure. It is the last line of defense between your family and a catastrophic tank failure. Respect it.
Why it starts dripping
- Worn valve: mineral deposits or a weakened spring prevent full seating — the most common cause, fixed by replacement.
- Excessive pressure: thermal expansion in a closed plumbing system (common with pressure-reducing valves or check valves) forces the valve open repeatedly.
- Overheating: a failed thermostat lets tank temperature climb until the valve does its job.
- Debris: sediment lodged in the valve seat after a flush or water-main event.
Why you must never cap it
We say this on every T&P call because we've seen capped discharge pipes: never plug, cap, or restrict the T&P discharge. Disabling this valve removes the tank's pressure relief — the results can be catastrophic. A dripping valve is a problem to fix, not to hide.
How we fix it properly
We don't just swap the valve and leave. We test static water pressure (expansion issues show up here), check thermostat calibration, verify the discharge pipe terminates safely near the floor, then install a new rated valve and test it. If pressure is the root cause, we recommend a thermal expansion tank so the new valve doesn't start dripping next month. The full job typically runs $150–$300.
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Frequently Asked Questions
Can I test the T&P valve myself?
You can lift the lever briefly to verify water flows — but old valves sometimes don't reseat afterward. If yours is already dripping, skip the test and call us.
How often should T&P valves be replaced?
Every 5–10 years, or at the first sign of weeping that isn't pressure-related.
My valve only drips at night — why?
Likely thermal expansion: pressure builds when no water is used overnight. An expansion tank usually solves it.
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