Inspecting Your Water Heater's Pressure Relief Valve

What the T&P Valve Does

A water heater is a closed, pressurized vessel. If a thermostat or gas control sticks on, water keeps heating and pressure keeps rising. The T&P valve is set to open at a temperature and pressure well above normal operation, dumping water through a discharge pipe so the tank cannot reach a dangerous point.

You will find it on the top or upper side of the tank, with a small lever and a pipe running down toward the floor. That discharge pipe should end a few inches above the floor or drain, with nothing screwed onto the end.

How to Test the Valve Safely

Testing once a year confirms the valve has not seized from mineral deposits. Here is the basic method:

• Place a bucket under the end of the discharge pipe. Keep your feet, hands and face clear, since the water will be very hot.
• Check that the cold water supply to the tank is open so the tank stays full.
• Lift the test lever partway for a few seconds. You should hear a rush of water and see it flow into the bucket.
• Let the lever snap back. The flow should stop completely within a few moments.
• Watch the end of the pipe for several minutes afterward to make sure it is not still dripping.

Safety Notes

Valves that have not been tested in years may not reseat after you lift the lever, leaving a steady trickle. That is not dangerous by itself, but it is a sign the valve needs replacing. Do not try to stop the leak by capping or plugging the pipe. Never block or remove a relief valve or its discharge line, and never replace one with a different type or rating.

If you lift the lever and nothing comes out, the valve may be stuck. Do not keep using a heater with a non-working relief valve. Lower the thermostat and call a plumber.

Warning Signs to Watch For

Even between tests, glance at the valve and pipe when you are in the basement. These signs deserve attention:

• Water on the floor near the discharge pipe, or rust stains at its tip
• A valve that opens on its own, especially after the heater runs a long cycle
• Crusty white or green mineral deposits around the valve body
• Hissing or spitting sounds from the valve
• Very hot water at the taps combined with any of the above

When to Call a Professional

A valve that discharges repeatedly is telling you something is wrong with temperature or pressure, not just with the valve. Causes include a faulty thermostat, high incoming water pressure, or thermal expansion in a closed system that needs an expansion tank. A plumber should find the cause before simply swapping the valve.

Our water heater service covers valve replacement, expansion tanks and full diagnostics, and annual valve checks are part of our preventive maintenance program. If you also want to confirm your thermostat setting, see our guide to water heater temperature settings.