TPR Valves

TPR Valves (temperature and pressure relief valves) are a safety device to protect homes and occupants. It has been said that water heaters are the most dangerous appliance in homes. Because water expands as it heats up, enormous pressure is exerted against the inside of the tank. If not for safety devices, that water can propel the water heater completely through the roof of a house, destroying the house, injuring occupants, and with scalding water sprayed around the home. Manufacturers, engineers, and even the Myth Busters have produced videos showing the explosive effects that could occur if water heaters did not have safety precautions.

Temperature and pressure relief valves are designed to prevent this possibility. They are rated to keep water inside the tank as long as neither the temperature nor the pressure exceed the designated safety limits. If a malfunction causes water to boil, produce steam, and subsequently enormous pressure – the valve will open and drain water until it is safe to stop. TPR valves should be drained safely – using proper pipe materials, appropriate size, limited elbows, and should terminate in an area that cannot splash and is visible from the water heater. The extensions should never be capped or connected to anything else.

Home inspectors licensed in Washington (and to my knowledge, 48 other states) do not operate or test the efficiency of TPR valves per our standards of practice. This is for many reasons, but the most notable for homeowners is that the valves tend to leak for several weeks after being operated for the first time in years. Homeowners should follow manufacturers instructions and test TPR valves as instructed to ensure they function and to loosen buildup that would lead to a leak after years of inactivity.

Too Long, Didn't Read Version: Be safe - make sure each of your water heaters incorporate a TPR valve that functions according to the manufacturer’s directions and have your plumber confirm it is properly drained for safety.

-Marshall Tramp, CPI, RMP


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Marshall Tramp, CPI, RMP
Author: Marshall Tramp, CPI, RMP
Top Notch Inspection Services llc
Serving Eastern Washington & Northern Idaho