That little pipe on the side of your tank exists for one reason: to dump water before pressure or temperature turns dangerous. When it starts dripping, homeowners split into two camps — ignore it, or panic. Do neither. Figure out which of the two causes you are dealing with, because the fix is completely different.
The two-minute version
A dripping TPR valve means one of two things. One: the valve itself is worn out — the spring is tired, the seat is crusted with minerals, and it weeps. Two: the valve is fine and it is doing its job, releasing water because temperature or pressure inside the tank is genuinely too high. Both need attention. Neither is fixed by ignoring it.
Cause 1: the valve wore out
TPR valves live in hot, mineral-heavy water for years. In Apache Junction, calcium and sediment crust onto the valve seat, the spring weakens with heat cycling, and eventually it cannot hold a seal at normal pressure. If your system pressure tests normal (40–60 psi) and the valve still drips, the valve is the problem — replace it with the correct rating for your tank.
Cause 2: it is doing its job
The valve opens around 210°F or 150 psi. If pressure is running high — 80+ psi at the gauge — or the thermostat is letting temperature run away, the valve discharges exactly as designed. Swapping in a new valve without fixing the pressure just buys you a new drip. The usual root causes: a failed expansion tank, excessive incoming pressure, or a faulty thermostat.
How to tell which one you have
Put a gauge on the system — that is the whole test. Normal pressure plus a drip means a bad valve. High pressure means chase the root cause first. While you are at it, tap the expansion tank: a dull thud instead of a hollow ring means it is waterlogged and no longer absorbing pressure spikes.
Never cap it — here is why
Capping or plugging the TPR discharge pipe removes the tank’s only protection against pressure buildup. It is one of the genuinely dangerous things a homeowner can do to a water heater. If the drip annoys you, fix the cause — do not plug the relief.
What we do about it
Pressure gauge first, expansion tank second, then a correctly rated valve if the valve is the failure — followed by a full-pressure test to prove the discharge stopped for the right reason. If your TPR pipe is wet, call (833) 713-2101 and tell us what the gauge says, if you have one.