Whether your water heater is natural gas, propane gas, or electrically powered, all makes, and models come equipped with a safety feature that’s called, the temperature and pressure relief valve. Without this safety device, the temperature or the water pressure inside your water heater tank could build to the point the tank ruptures causing all sorts of damage to your home.
In this post, let’s give a solid definition of the temperature and pressure relief valve on your water heater, how they work and how to maintain one to keep its safety feature in place protecting you, your family, and your property.

What Role Do a Temperature and Pressure Relief Valve Play in Your Water Heater?

The Temperature and Pressure Relief Valve sometimes called the T&P Valve or the ‘Pop-Off’ Valve is a factory-installed safety feature of any water heater regardless of make or model. It is usually located on the top of your water heater or the side, close to the top. Its location on the water heater is directly related to the safety features it offers.

When there is a problem with the temperature or pressure inside the water heater, the problem usually results in both temperature and pressure building up. Since heat rises, the steam and pressure build-up is always near the top of the water heater. Once the temperature or pressure reaches a certain ‘unsafe level’ the valve ‘pops’ open releasing the steam and pressure before the tank ruptures causing catastrophic damage to people and property.

There should be a plastic (CPVC) or iron pipe installed on the outlet of the T&P Valve to divert steam and water pressure safely outside away from both you and your home.
The valve remains ‘open’ until the temperature and pressure reach safe levels where the valve will then ‘pop’ closed. In a normal operation, when the valve closes it is seated properly inside the valve, and the steam and water pressure escaping then stops altogether.

How Does the Temperature and Pressure Valve Know When to Open?

As mentioned above once the temperature, pressure, or both reach unsafe levels the T&P Valve is activated. There is a seal inside the T&P Valve housing that essentially opens and closes per its design. When steam, water pressure, or both reach unsafe levels the pressure build-up will force that seal to open and the internal spring on the side of the seal opposite the steam and pressure will allow the seal to fall back into place when the pressure incident has subsided.

Factory-installed T&P Valves will open as advertised when the water temperature gets to 210 degrees Fahrenheit or the water pressure inside the tank reaches 150 psi (pounds per square inch). Municipal water supply usually comes into your home at 40 to 80 psi and experts have argued that anything over 60 psi is too much.

The water temperature on the water heater should not be set any higher than 100 degrees. Anything beyond that can scald your skin so try to keep the water temp at 80 to 95 degrees Fahrenheit.

If your water heater’s T&P Valve activates there is an underlying cause that is contributing to this matter.

How to Test the Temperature and Pressure Relief Valve

If you are wondering if your T&P Valve is operating correctly, there is a simple test you can perform to check the valve’s operation. If the discharge pipe attached to the valve runs outdoors or is just terminated under your floor into the crawlspace this might pose an issue when checking the T&P Valve for correct operation.

If the discharge pipe end is where you can see it, place a bucket under it to catch the hot water you are about to release during this test.

With the catch bucket in place, grasp the lever on top of the valve and begin to slowly lift it. As soon as the internal seal is broken hot water should begin flowing out of the discharge pipe. Once you have determined hot water is flowing through the valve, release the lever.

The lever should ‘pop’ back in place and the hot water should stop flowing. If the lever does not completely reseal the internal opening, there may be a mineral build-up in the valve from the water supply causing the valve not to completely seal. This is a common issue within T&P Valves and should be promptly addressed by a licensed plumber familiar with these issues.

If you perform this test and the valve operates in a normal fashion, congratulations, you now know how to test your water heater’s T&P Valve and you should periodically check it from now on to avoid bigger and uglier issues from a failed T&P Valve!

Keep a Watchful Eye on Your Water Heater’s Temperature and Pressure Relief Valve

You might want to get in the habit of keeping an eye on the T&P Valve just to make sure everything is running normally with your water heater.

If you notice water coming from the discharge pipe on the T&P Valve it could mean two possible conditions;

  1. Everything is normal, and your valve is just releasing a bit of pressure built up inside the tank, or
  2. The T&P Valve has opened and cannot properly close and reseal

If you notice your T&P Valve is constantly releasing steam and/or pressure, you need a professional plumber to diagnose the cause of this pressure build-up as soon as possible.
If the valve can’t reseal and water is escaping through the valve, it could be the scaly build-up mentioned earlier, and the valve could need to be replaced by a professional plumber.

How Old is Your Water Heater?

The average lifespan of a residential water heater regardless of its heat source is between 6 and 13 years. That being said, if your water heater is 10 to 12 years old, your water heater could be living on borrowed time!

Why not take a moment and get your water heater and its T&P Valve checked out by a professional plumber, Allbritten is always here to take your call!

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