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T&P Relief Valve: An Important Water Heater Safety Device

T&P relief Valve

The T&P Relief Valve, short for Temperature & Pressure Relief Valve, is a critical safety device on your water heater. This valve may sit quietly unnoticed on your water heater, but it has a very important purpose: To keep your heater from exploding! If your T&P relief valve is properly functioning and your tank has an excess of pressure, the valve will open to relieve the pressure and you may think you have a leaking water heater, the puddle of water on the floor will be near the discharge tube and is a sign your valve is working properly.

When the hot water within your tank reaches a temperature of 210 degrees Fahrenheit, or the internal tank pressure exceeds 150 psi (pound per square inch) the T&P valve is designed to open and relieve the pressure within the tank. Once the pressure returns to a safe level, the valve automatically closes. Checking your T&P valve is one of several preventative maintenance tasks you should perform.

When Your T&P Relief Valve Opens

The T&P relief valve is usually located on the side of your tank, but it can also be on the top. There is a long pipe (often called a drain or discharge pipe) that is attached to the valve and runs down the side of the heater and ends a few inches above the floor.

T&P valves are required to have a drain pipe, however, on occasion the pipe may not have been installed. If your heater does not have a drain pipe attached, you should hire a plumber or add one yourself.

When the T&P valve activates, extremely hot water will be discharged. It is critical from a safety standpoint that the water is delivered to the floor. Without a drain pipe the discharged water will spray out from the T&P valve.

If you notice water around your T&P valve or at the base of the drain pipe there are two possible problems that may have occurred:

  • A faulty valve
  • The valve is properly working and there is too much pressure within the tank.

It's critical to figure out what caused the valve to trigger. The problem should be addressed immediately since it's a clear indication of an abnormal condition.

Faulty Valve​

T&P relief valves wear out and from time-to-time need to be replaced. But sometimes debris becomes lodged in the valve and prevents it to properly closing. Before assuming that your valve is defective, first try flushing the valve.

Flush the T&P Valve​

  • Turn OFF the power and incoming water to the heater.
  • Place a bucket under the T&P drain pipe.
  • OPEN the T&P valve by flipping the tab on the valve so that its pointing straight.
  • Water will flush thru the valve. Use caution as the water will be hot.
  • CLOSE the valve.

Debris is a common reason your T&P valve malfunctions. However, after drying the area, if you still notice moisture, the valve itself is likely defective and needs to be replaced. 

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Replace the T&P Valve

  • Turn OFF the power and incoming water to the heater.
  • Drain the water from the tank so that the water level is below the T&P valve. Check this by opening the valve. If water is released, you need to drain more water.
  • OPEN a hot water faucet to allow air to enter the tank. This will assist with draining.
  • Turn the valve counter-clockwise with a wrench.
  • Remove the defective valve.
  • Wrap the threads of the new T&P relief valve with Teflon tape.
  • Insert the new valve into the water heater and turn clockwise until it is firmly locked in place.
  • OPEN the cold water supply to the heater and fill the tank. Do not turn on the power until the tank is full of water.
  • Replace the drain pipe to the T&P valve.
T&P Relief Valve
Rheem SP8346 Temperature and Pressure Relief Valve with 3/4-Inch NPT

How to Replace a T&P Relief Valve

Properly Working T&P Valve

If your T&P valve is working properly it is opening to relieve the pressure within the tank. You can rest assured that the valve is functioning as it should, however, there is something wrong with your water heater that is causing the temperature to exceed a safe limit. Some of the causes could be:

  • Thermal expansion (when water is heated it expands).
  • High system pressure.
  • High temperature relief.
  • Temperature gauge set too high.

You can try turning down the temperature on the thermostat, but you really should hire a professional plumber to investigate the problem. 

T&P Valve Maintenance

The service life of a T&P valve is generally 3 years. However, it should be checked at least once a year. Many manufacturers recommend removing and visually inspecting the valve, as it can develop a build-up of corrosion. 

How to Test Your Temperature & Relief Valve

  • Place a bucket under the T&P drain pipe.
  • Lift the tab on the valve to allow water to flow. The water released will be hot.
  • Close the tab on the valve once the water becomes clear. Usually this takes only a few seconds.
  • If the T&P relief valve continues to release water, quickly lift the tab up and down several times to help re-seat the valve.
  • If after attempting to re-seat the valve, the T&P still leaks, the valve needs to be replaced.

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