How to Check Your T&P Valve


The T&P valve is designed to open and release pressure inside the tank if the temperature or pressure inside gets too high. If your T&P valve is either always leaking or, if you test it and no hot water comes out, you should replace the valve immediately.

Mineral or salt buildups, rust, corrosion, or mechanical equipment failure can cause T&P valves to malfunction. A failed or malfunctioning T&P valve can lead to quite a mess and in some extreme cases, can lead to catastrophic damage.

water heater maintenance - check t&p valve

Think about it this way: if the T&P valve is designed to release pressure in the water heater but doesn’t do its job, internal pressure will continue to build and build until the water heater actually explodes. While very rare, water heaters have been known to rocket through the roofs of houses, leaving 50 gallons of boiling hot water and steam in their wakes. What a mess!

To see how it actually happens, watch this MythBusters episode where they simulate a water heater explosion.

However, there are signs you can look for before your water heater turns into a bomb. In your home, the Pressure Relief Valve, or PRV, is designed to regulate internal pressure in your plumbing. When the T&P valve on your water heater isn’t working, that extra pressure is sent throughout the house. Therefore, all of the pipes and appliances in your house will expand and contract with the pressure, including the water heater tank. An expanding and contracting tank can crack the glass liners inside, which means the tank is now compromised, which can lead to failure. So, you can troubleshoot for a problematic T&P valve if you have leaking fixtures or experience a lot of pressure in your appliances connected to the plumbing system in your home. The good news is that when you turn on a faucet, this relieves system pressure; however, this is also why most water heater failures happen when people are out of town. No one is turning on faucets to relieve tank pressure.

So, let’s make sure we check that T&P valve, shall we? Keep in mind that these instructions are designed to help the do-it-yourself homeowner take care of their own water heater. However, if you read the following instructions and feel like this might be a bigger job than you want to take on, call a plumber you trust to help.

Complete these 4 steps FIRST before performing ANY maintenance on your water heater to avoid the risk of water damage, scalding burns, electrocution, or explosion: 

  1. Disconnect power at the breaker for an electric water heater.  
  2. Shut off the gas valve for a gas water heater and make sure the pilot light is extinguished.
  3. Close the cold water inlet valve or main water supply. 
  4. Turn on the hot water at a faucet somewhere in the house. No water will come out of the faucet; this simply helps to relieve the pressure inside the water heater tank. 
With the power and the cold-water supply off, check the T&P valve by placing a bucket under the pipe connected to the valve on the top or side of the tank. Lift the valve's tab to let some water out into the bucket. You should be able to hear a slight rush of air or see some water and vapor exit through the pressure relief valve. If not, it needs to be replaced. Now, let go of the valve. If water keeps flowing, this is another indicator that your valve needs to be replaced. 
Drain the tank halfway and, using a pipe wrench, remove the discharge pipe and unscrew the valve from the water heater. You’ll need to be aware of the stem length of your existing valve when you go to purchase a replacement to make sure it’s the right one. Screw the new valve into place, tightening it with a wrench. Reattach the discharge pipe and refill your water heater tank. 
If at any time you feel overwhelmed, have questions or concerns, call a plumber you trust for help. If you don’t have a trusted, licensed plumber and are in the Utah market, call Any Hour Services and we’d be happy to send a plumber to your home to assess your system, perform any maintenance for you, and answer any questions you might have.

water heater maintenance - temperature pressure relief valve



Author: Amber Smith-Johnson
Copyright © 2019 by Any Hour Services


Jul 14th 2019

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