Common leaks
Water heater relief valve (T&P) leaking
If the leak is at the T&P (temperature & pressure) relief valve, do not cap, plug, or block it. It's the device that keeps the tank from rupturing. Lower the thermostat and call a plumber.
The temperature & pressure (T&P) relief valve is the single most important safety part on a water heater. When it drips, it's telling you something — so the fix is to listen to it, not silence it.
Get your specific answer Open the triage with a relief-valve leak pre-selected — add the age and type for the verdict and cost.What the valve does
The T&P valve opens and releases water through a discharge pipe when the tank's temperature climbs past about 210 °F or its pressure past about 150 psi. That's the last line of defense against a tank rupturing. If you cap or plug a dripping valve to stop the mess, you remove that defense — which is why you never do it.
Why it's leaking
A drip means one of two things:
- The valve is worn out. After years of sitting, the seat can weep. Replacing the valve fixes it — about $150–$350 with a plumber, or a $15–$50 part.
- It's doing its job. Excess pressure or heat is opening it — from a thermostat set too high, thermal expansion on a closed plumbing system with no expansion tank, or high household water pressure. Here the valve isn't the problem; it's the messenger.
The real fix
Lower the thermostat first, then have a plumber replace the valve and check the cause. If it's thermal expansion, the fix is a small thermal expansion tank (about $200–$450 installed) or a pressure-reducing valve — not a new water heater. Follow the shutoff steps if it's discharging steadily, and use the triage to weigh repair vs replace against the unit's age.
Relief-valve questions
Why is water dripping from the temperature and pressure (T&P) relief valve?
The T&P valve is a safety device that opens to release water when the tank's temperature climbs past about 210 °F or its pressure past about 150 psi. A drip means either the valve is worn out, or it's correctly relieving excess pressure or heat caused by a too-high thermostat, thermal expansion on a closed plumbing system, or high household water pressure. Never cap, plug, or block a leaking T&P valve — that's what it's there to prevent. Lower the thermostat and have a plumber replace the valve and find the cause.
Will a leaking water heater explode?
Almost certainly not. An explosion takes two safety systems failing at the same time: the thermostat or high-limit switch has to fail and let the water superheat, and the T&P relief valve has to be blocked, seized, or capped so the pressure can't escape. Industry safety guidance treats that combination as highly unlikely on a modern heater, and a leak on its own doesn't cause it — a T&P valve that's discharging is the safety system doing its job. The one thing that genuinely raises the risk is capping or plugging a dripping T&P valve, so never do that. If it's discharging, lower the thermostat and have a plumber find out why it opened.
What should I do first when my water heater is leaking?
Follow the safe order: (1) cut the gas or power to the heater; (2) close the cold-water shutoff on the pipe entering the top of the tank, or your home's main water valve if you can't reach it; (3) contain the water — you don't need to drain the tank for a leak; (4) leave the T&P relief valve alone if that's where the leak is; and (5) call a licensed plumber if it doesn't stop, the tank is leaking from its body, or you're unsure. Enter your leak's location in the triage tool for the specific cause and next step.
Should I repair or replace a leaking water heater?
It comes down to where it's leaking and how old it is. A leaking connection, drain valve, or relief valve on a heater under about 8 years old is usually worth repairing. Past roughly 8–12 years a storage tank is near the end of its service life, so a repair competes with a replacement you'll need soon anyway. A tank leaking from its body is a replacement regardless of age. The triage tool weighs your leak location against the unit's age to give you a specific repair-or-replace call.
How much does it cost to replace a water heater?
Installed replacement in 2026 typically runs about $700–$1,800 for an electric tank, $1,000–$3,000 for a gas tank, and $1,200–$4,500 for a tankless unit — electric at the low end of that range, gas at the high end — with labor making up roughly 30–50% of the total. A straightforward same-location swap is at the low end; relocating the unit, upsizing gas or venting, or bringing old connections up to code pushes it higher. These are typical ranges, not quotes — get two or three local estimates.