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How to Replace a Water Heater Temperature & Pressure Relief Valve


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Tank-style water heaters have a very important safety device called the Temperature & Pressure (T&P) Relief Valve. This valve is designed to release pressure within your water heater in the event the pressure reaches an unsafe level.

Testing and maintaining this valve is a important maintenance task which can easily be done by the homeowner. This article will show you how to test your T&P valve and replace it should the valve be faulty. Performing regular maintenance on your water heater will not only extend it's service life, but it can also prevent an unsafe situation.

Role of the Temperature & Pressure Valve

The Temperature & Pressure (T&P) Relief Valve should be tested at least once a year. This valve is a safety device to prevent your hot water heater from exploding. Most are designed to activate if the water temperature in your tank exceeds 210° 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. If you notice water around the T&P valve, the valve is fulfilling it's role as a safety device. But, keep in mind, that it's important to determine the reason the T&P valve was triggered. 

There can be several reasons for water discharge, but regardless of the cause, it's a clear an indication of an abnormal condition, and it should be immediately addressed.

Possible Causes:

  • Thermal expansion (when water is heated it expands
  • High system pressure
  • High temperature relief
  • Temperature gauge is set too high
  • Or something else in the water heater that's causing the temperature to exceed a safe limit

Another cause of a leak from the T&P valve could be high water pressure in the municipal system or some sort of backflow preventer around the water meter or main shutoff. If you remove your T&P valve and see no signs of corrosion inside the valve it's possible this is your problem. You’ll need a licensed plumber to diagnose and handle these more serious problems.

Preparing to Test Your T&P Valve

Before testing your T&P valve, we highly recommend the following:

  • Know where the shut-off valve is located for the water heater's incoming water.
  • Know where the fuel shut-off is located (gas or electric).
  • Do the test during regular business hours. If you have a problem and need to call a plumber, it'll be less expensive and easier to arrange a visit.
  • If your T&P valve hasn't been tested in years, be prepared. It may get stuck in the open or closed position. If this happens, shut off the incoming water supply and replace your T&P valve. We recommend calling a plumber.

How to Test a Temperature & Pressure Relief Valve

The T&P valve should be checked at least once a year. However, it's important to note that the service life of a T&P valve is typically only 3 years. Even if the valve visually looks to be in good working order, most manufacturers recommend that it's removed and inspected at minimum, every few years.

T&P valves have a tendency to develop a build-up of corrosion, which can eventually prevent them from performing their safety role. Although you can replace the Temperature & Pressure Relief Valve yourself, we highly recommend hiring a qualified plumber.

Testing the T&P Valve: Step-by-Step

Lift the Test Handle - The T&P valve has a small test handle on the valve. When lifted, the valve will open and allow water to flow through the runoff tube (also called overflow pipe). Be sure to clear the area around the floor drain before opening the valve.

  • If the test handle does not open relatively easily the T&P valve is most likely faulty and needs to be replaced.
  • If the test handle lifts, but it does not open the T&P valve to allow water to flow, the valve is faulty and needs to be replaced.

Flush the T&P Valve - Assuming that your T&P valve is not faulty, allow the water to flow through the valve for a few seconds until it runs clear. 

Close the T&P Valve - Once the water flowing through the runoff tube is clear you can close the valve by releasing the test handle.

  • If the T&P valve continues to run, lift the test handle up and down quickly. This often helps reseat the valve.
  • If the T&P valve continues to leak, it should be replaced.

Watch the Video

How to Replace a T&P Valve

If you're comfortable tackling these types of projects, replacing a T&P valve is absolutely something that you can do yourself. However, we recommend hiring a professional plumber if you're not a DIY kind of person. The T&P valve is an important safety device and it's critical that it's installed correctly.

A best practice is to drain fully drain your tank when changing the T&P valve so that the tank can be flushed of sediment, although, this is not necessary to do at this time. The instructions below cover how to change the valve without fully draining your tank.

Rheem SP12574 Temperature and Pressure Relief Valve

You'll need to purchase a new T&P valve. This one is made by Rheem

Changing a T&P Valve: Step-by-Step

Turn Off The Power - Before working on your water heater flip the circuit breaker off (electric model) or turn the gas control valve to the pilot setting. You should NEVER work on a water heater that has not been turned off.

Connect a Garden Hose - Connect a garden hose to the drain valve located at the bottom of your water heater. Run the other end of the hose to a floor drain, sink, or outside. Do not open the drain valve yet.

Shut Off the Incoming Water - Close the shut off valve on the cold water inlet supply line so that no water will enter the water heater. Open a hot water faucet to relieve the pressure within the tank (then close the faucet). 

Open the Drain Valve - Open the drain valve and allow the water to flow through the garden hose. If your tank has an excessive amount of sediment build-up, it may not drain. Read this article to unclog your drain valve

Drain the Water - If your T&P valve is mounted on top of your water heater, you'll need to drain about 1-gallon of water. If the valve is mounted on the side, the water level will need to be below the T&P valve, approximately 10-gallons of water. Be careful, the water will be hot!

Remove the Runoff Tube - Before you can remove the faulty T&P valve, you'll need to remove the runoff tube from the valve. In some cases, you'll need to cut the copper pipe with a copper pipe cutter, sometimes you'll be able to simply unscrew the tube. It depends on how your water heater was installed. 

Remove the Faulty T&P Valve - Using a wrench, unscrew the faulty T&P valve and remove it from the water heater. 

Install the New T&P Valve - Wrap your new T&P valve with teflon tape. Use at least 6 wraps around the valve in the direction that the valve will be screwed back into the heater. Insert the new valve into the water heater and double check that the test handle is closed. Use a wrench to secure the valve in place.

Connect the Runoff Tube - Reconnect the runoff tube to the T&P valve. If you have a copper runoff tube, this article will show you what to do.

Open a Hot Water Faucet - Leave the faucet open until there's a steady stream of water flowing.

Open the Shut Off Valve - Open the shut off valve on the cold water inlet supply to allow the water heater to fill. 

Open the T&P Valve - Lift the test handle on the T&P valve to open the valve until a steady stream of water flows through the runoff tube. Then, check your hot water faucet and turn it off once there's a steady stream of water. 

Turn the Power On - You can now turn your electric water heater back on at the circuit breaker. If you have a gas heater, you can turn the gas back on at the gas control valve.

Check for Leaks - Check that your T&P valve is tight and that there are no leaks. 

Watch the Video

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