Testing Your Water Heater Temperature and Pressure Relief Valve

Did you know that your water heater will function better and be safer if you do a little routine maintenance? Some water-heater experts recommend testing every six months. More frequent testing can reduce the chance of a leak caused by mineral and corrosion buildup. The temperature and pressure relief valve (TPR valve) opens to release pressure buildup in the water heater when the temperature or the pressure get dangerously high, preventing a possible explosion.

A buildup of mineral salt, rust, and corrosion can cause a TPR valve to freeze up and become nonoperational. To test the valve to ensure that it’s working properly, simply raise and lower the test lever several times so it lifts the brass stem that it’s fastened to. Hot water should rush out of the end of the drainpipe. If no water flows through the pipe or you get just a trickle, replace the valve.

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However, if a leak results immediately after a test, simply operate the test lever several times to free lodged debris that may be preventing the valve from seating properly. If the valve is doing its job and hot water is dripping or spewing out of the TPR drain valve, turn down the temperature on the water-heater controller and/or turn down the water pressure.

Here are other things to pay attention to:

  • The pipe leaving the relief valve should be the same diameter as the exhaust port of the valve — usually 3/4 inch. Moreover, the pipe should be made of a material that is not adversely affected by heat, such as copper. If the pipe is undersized or not heat-resistant, replace it with copper or have a plumber do it for you.

  • The TPR drainpipe should travel in a slightly downhill direction from the valve to the point where it terminates. It should end outside the house at 6 to 24 inches above the ground. If the drainpipe moves uphill and then downhill, water could get trapped against the outlet of the valve and corrode it shut. If the drain line had a trap or a low spot, water could freeze. And even if the valve works, pressure would be captured and an explosion might occur. If the drainpipe isn’t properly configured, call in a plumber to correct it.

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