This Old House plumbing and heating expert Richard Trethewey explains the extreme importance of maintaining your water heater's temperature-and-pressure relief valve.

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Temperature and pressure relief valves (TPR's) must be installed on all water heaters.

It is critical that a leaking or defective TPR valve is replaced immediately. Replacements can be purchased at home centers and plumbing supply stores.

It is also important that TPR valves are not plugged or tampered with in any way.

Richard also showed the Safe Plug Relief valve, a device that is designed to prevent tampering with the TPR valve. It is manufactured by Dulac Plumbing Innovations Corp. [http://www.dulacdpi.com/]

Photographs of the home damaged by a water heater explosion were provided by Anchor Inspections of Phoenix, AZ [https://bit.ly/3f3J2Nn] and by the City of Phoenix.

Steps for How and Why to Maintain a Temperature-and-Pressure Valve:
1. Regardless of the type of water heater, whenever water is heated, it expands. And the water-heating system must accommodate the expansion. Otherwise an explosion could occur.
2. Expanding water can move out the cold-water line. However, if there's a pressure-reducing valve mounted near the water main, the valve can block expansion.
3. Adding an expansion tank to the heater can accommodate a certain amount of expansion.
4. All water heaters are equipped with a thermostat that controls the water temperature.
5. If the thermostat fails and pressure builds up in the tank, the temperature-and-pressure relief valve will open and discharge built-up steam and hot water.
6. Temperature-and-pressure relief valves should always be connected to a discharge pipe that extends down to the floor.
7. Once a year, open the valve to flush out minerals and sediment.
8. Never install a plug into a temperature-and-pressure relief valve. And if you see a plug in the valve, turn off the water heater and immediately call a plumber.
9. To prevent someone from plugging the valve, install a tamperproof adapter.
10. If you see water dripping from the discharge tube, turn off the water heater and call a plumber. The temperature-and-pressure relief valve should be replaced.

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How and Why to Maintain a Temperature-and-Pressure Valve | Ask This Old House
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