See water dripping from the small pipe on the side of your water heater? That's the discharge pipe of the temperature-and-pressure (T&P) relief valve — the safety device standing between you and a potential tank rupture. Take it seriously, but don't panic: here's the full picture.
What the T&P valve does
It's a spring-loaded valve set to open at 150 PSI or 210°F, dumping scalding water out the discharge pipe before pressure can split the tank. When it drips, it's either working correctly against excess pressure/temperature, or failing itself with a worn seat or mineral-fouled seal.
The three common causes
1. Thermal expansion. In closed plumbing systems (with a check valve or PRV), heated water has nowhere to expand — pressure spikes and the valve weeps. The fix is an expansion tank, not just a new valve. 2. Excessive incoming pressure. Municipal pressure above 80 PSI stresses everything; a pressure-reducing valve solves it. 3. A worn valve. Mineral crust on the seat — rampant in Apache Junction — prevents sealing. Replacement is quick and affordable.
What to do right now
- Place a bucket under the discharge pipe termination — never cap or plug the pipe.
- Note whether it's a slow drip or a steady stream (a stream is more urgent).
- Check if your water feels unusually hot — overheating needs immediate attention.
- Call (833) 713-2101 — we test pressure first so we fix the cause, not just the valve.
What never to do
Never plug, cap, or restrict the discharge pipe. Never ignore a valve that pops open repeatedly. And never assume a new valve alone fixed it if the underlying pressure issue remains — that's the mistake we see most.
Related Questions
Can I replace a T&P valve myself?
It's physically simple but safety-critical: wrong rating, wrong installation, or an unaddressed pressure problem can be dangerous. It's an affordable pro job — let a licensed tech handle it.
Why did my new T&P valve start leaking too?
Because the valve wasn't the root cause. Thermal expansion or high incoming pressure will defeat every new valve until an expansion tank or PRV addresses it. We test for this first.
How much does T&P valve replacement cost?
Typically $150–$300 in Apache Junction, including the valve and testing. If an expansion tank is needed, the combined job runs $350–$650.