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Temperature/Pressure Relief Valve

T/P Relief Valve

The Temperature/Pressure (T/P) Relief Valve should be tested at least once a year. This valve is a safety devise to prevent your hot water heater from exploding. Most are designed to activate if the water temperature in your tank exceeds 210 degrees Fahrenheit, or the pressure in your tank exceeds 150 psi. When your water heater is functioning properly, the T/P valve and surrounding area should be dry.

Should you see water around the T/P valve, your T/P valve is fulfilling its role as a safety device. But it is important to find out what caused the T/P valve to trigger. There can be several reasons for water discharge, but it is clearly an indication of an abnormal condition, and should be immediately addressed. Some of the causes could be due to thermal expansion (when water is heated it expands), high system pressure, high temperature relief, temperature gauge set too high, or something else in the water heater causing the temperatures to exceed a safe limit.

Testing Your Temperature/Pressure Relief Valve

Prior to testing, it’s a good idea to do the following:

  • Know where the shut-off valve is located for incoming water to your water heater.
  • Know where the shut-off is located for fuel (gas or electric).
  • Know and have available the phone number for your plumber (preferably test during business hours. Should you have a problem and need to call a plumber it will be less expensive and easier to arrange a visit).
  • If your T/P Relief Valve has not been tested for years, be prepared, it may get stuck in the open or closed position. Should this happen, shut off the incoming water supply and call your plumber.

How to Test

  1. Clear the area around the floor drain and overflow pipe.
  2. Lift the test handle, opening the valve and allow the water to flow until it is clear. It usually takes a few seconds.
  3. Release the test handle, closing the valve.
  • If the T/P Relief Valve continues to run, lift the test handle up and down quickly. This often will help reseat the valve.
  • If the T/P Relief Valve continues to leak, it should be replaced.

The T/P valve should be checked at least once a year. However, the service life of a T/P valve is usually only 3 years. Even if the valve visually looks to be in good working order, most manufacturers recommend that it is removed and inspected. It is not uncommon for the T/P valve to develop a build-up of corrosion, which will eventually prevent it from performing its safety function. The Temperature/Pressure Relief Valve (T/P) should only be replaced by a qualified plumber.