T&P Relief Valve Leaking? Causes, Dangers, and Fixes

The temperature-and-pressure relief valve is the most important safety device on your water heater — and when it drips, it's sending a message. Here's how to read it.

What the T&P valve does

If water in the tank overheats or pressure spikes, the T&P valve opens to discharge scalding water through its pipe — preventing the tank from becoming a pressure vessel. It's the last line of defense against a catastrophic rupture, which is why it must never be capped, plugged, or removed.

Cause 1: The valve itself has failed

Most common. The spring weakens with age and mineral deposits prevent a full seal, so the valve weeps continuously. The fix is straightforward: replace the valve with a correctly rated new one, typically a same-visit job.

Cause 2: Excess system pressure

If a new valve still discharges, your plumbing pressure is genuinely too high — often from thermal expansion in a closed system (check valve or pressure-reducing valve at the meter) with no expansion tank to absorb it. The real fix is an expansion tank, not a stronger valve.

Cause 3: Overheating

A thermostat stuck on high can push water toward dangerous temperatures, and the T&P does its job by dumping it. If discharge water is scalding and the tank feels excessively hot, treat it urgently: shut the heater down and call.

Why this matters more in older homes

In Attleboro's vintage housing we find T&P discharge pipes that terminate mid-air, drain into walls, or were "temporarily" capped years ago — each a genuine scalding and flooding hazard. When we replace a valve, we verify the discharge line runs to within inches of the floor, because a safety device with nowhere safe to discharge isn't safe.

What to do right now

Note whether the dripping is constant or only after heavy hot-water use, check the discharge pipe's condition, and never plug it. Then call us at (833) 713-2101 — we'll test whether it's the valve or the pressure, and fix the actual cause.