How to Replace Water Heater Temperature and Pressure Relief Valve


A temperature and pressure relief valve (T&P valve) is an essential safety component fitted on a water heater. This device plays a critical role when the pressure within the tank surpasses a specific threshold. In such cases, the valve opens, thereby relieving the accumulated pressure. Should your water heater's burner continuously heat without a properly functioning relief valve, it could result in a catastrophic event, including the explosion of the water heater.

This danger was demonstrated in an episode of Mythbusters. The presenters removed the relief valve and other safety devices and continued to heat the water heater. The result was a dramatic projection of the water heater, shooting up like a rocket and reaching an astounding height of over 500 feet.

Although water heaters incorporate additional safety measures to mitigate such incidents, the significance of a functional T&P relief valve cannot be overstated. It is therefore vital to ensure its effectiveness through regular testing and maintenance. This article will serve as a guide, helping you understand how to test, repair, and replace a temperature and pressure relief valve, thereby ensuring your water heater's safe and efficient operation.

Test Existing Valve

The temperature and pressure relief valve can be found on the top section of your water heater tank. This valve is distinguished by its small handle and an attached discharge tube or downspout. This downspout is designed to channel scalding water safely downwards, preventing injury in the event of valve operation.

To test the valve, first prepare a bucket and position it beneath the discharge tube. Subsequently, gently lift the small handle briefly to open the valve, and then pull it back down to close it. Do not be concerned if water continues to flow for a few moments after you've closed the valve. This is merely residual water draining due to the discharge tube's length. However, if the water persists in dripping after a period, for instance, 10 seconds, it indicates that the valve may be faulty and in need of replacement.

How to Replace Temperature and Pressure Relief Valve

It is easy to replace the relief valve. It simply involves removing the old valve and installing the new valve with a few obvious steps in between.

Tools You Will Need

Teflon Tape

Pipe Joint Compound

Pipe Wrench:

Small bucket

Finding the Right Replacement Valve

In order to purchase a suitable replacement, it's crucial to ascertain the precise specifications of your existing valve. These details are typically inscribed on the relief valve currently installed on your water heater. We recommend taking a photograph of these specifications for easy reference when searching for a replacement.

Ideally, you should aim to purchase an identical valve from the same manufacturer. This can often be accomplished by entering the model number into a search engine, which should guide you to the exact valve you need.

However, if the exact model is unavailable, an alternative relief valve may suffice, provided it aligns with certain key criteria. It should have a BTU rating that either matches or exceeds that of your original valve. The fitting size should be the same, and the valve should be tested to the same temperature and pressure values. Moreover, the temperature probe and extension length should match those of your original valve, and the length of the fitting should be equivalent to or longer than the original.

If you find yourself uncertain or overwhelmed by the process, don't hesitate to consult with professionals at your local plumbing supply store. By showing them the photograph of your valve's specifications, they should be able to assist in identifying an appropriate replacement.

Turn off the Power Supply

Adjust the thermostat to either 'Pilot' or 'Vacation' mode. Alternatively, you can switch off the thermostat and close the gas valve, but bear in mind that this will necessitate relighting the pilot flame afterwards.

Turn off the cold water supply

At the top of the water heater tank, there should be two pipelines. One of them has a valve. Turn the valve so that it is perpendicular to the pipeline.

Drain the water heater

Considering that your water heater tank is filled with water, an immediate removal of the relief valve will lead to a burst of water from the tank. Therefore, the initial step is to drain several gallons of water from the tank until the water level is below the relief valve's position.

The drain valve is typically located towards the bottom side of the tank. To drain the water, you'll need to attach a garden hose to this valve. This can typically be done by screwing the hose onto the valve. Once securely attached, adjust the drain valve such that it is in line (parallel) with the garden hose pipe. This adjustment essentially opens the valve.

As you open the valve, you may hear some noise; this is completely normal and simply the sound of pressure being relieved within the system. However, due to the air and water-tight nature of the tank, no water will drain out just yet.

To enable the water to flow out, it's necessary to introduce air into the tank. This can be achieved by opening a hot water faucet elsewhere in the house or by opening the relief valve on the tank. We recommend the latter option as it provides a more accurate indication of when the water level has fallen beneath the relief valve.

After ensuring that the bucket is still in place under the discharge tube, open the relief valve. You'll likely hear a gurgling sound as water and air are displaced from the tank. As long as this gurgling persists, the water level remains above the relief valve's position.

As the water level drops, the sound will transition to a smoother, quieter sound - akin to air quietly escaping. When you detect this change, you can close the drain valve.

With the water level suitably lowered and the tank depressurized, you're now ready to safely remove the temperature and pressure relief valve.

Remove the temperature and pressure relief valve

Step 1: Remove the Discharge Tube:

The discharge tube is the pipeline attached to the temperature and pressure relief valve. In an ideal scenario, the plumber would not have tightly affixed the discharge tube to the tank. If so, the first step is to detach this pipe from the tank. To do this, unscrew the tube from the tank with a wrench, rotating it until it comes free from the relief valve.

Step 2: Remove the Temperature and Pressure Relief Valve:

After removing the discharge tube, it's time to remove the pressure relief valve from the tank. Use a wrench to rotate the valve in a counter-clockwise direction until it comes out of the tank.

Install the replacement valve

After removing the old valve, prepare the new valve for installation. Begin by wrapping Teflon tape around the new valve's threads. This ensures a good seal and helps prevent potential leaks. With the tape applied, spin the new valve into the tank's opening by hand initially, to ensure it's correctly aligned and threads smoothly. Once it's started, use a wrench to tighten it further, but be careful not to over-tighten and potentially damage the threads.

After the new valve is secured, reinstall the discharge tube by spinning it back into the relief valve with the wrench.

Well done! You've successfully replaced the temperature and pressure relief valve on your own. But before you reward yourself with a well-deserved sandwich, it's crucial to restart your water heater.

Restart the water heater

Detach the hose from the drain valve, and open a hot water faucet within your house. Next, open the cold water supply valve on the tank. You'll hear air escaping from your hot water faucet initially, followed by water flow as the tank refills. Once the water flows out in a steady, smooth stream, you can close the faucet.

Test the New Temperature and Pressure Relief valve

Ensure the new relief valve is functioning properly by testing it using the same procedure as earlier. If the valve operates as expected, then you have successfully completed the process. Now it's truly time to reward yourself with that sandwich!