Why Is My Water Heater Overflowing?

Your water heater comes with a safety feature called a “temperature pressure relief valve.” When the pressure builds up inside of your water heater, the TPR valve releases it. The TPR valve is attached to a discharge pipe that aims the overflow at the floor or ground where your hot water heater is positioned.

If the TPR valve were to malfunction, pressure inside the tank could cause the tank to explode, causing terrible damage to your home. You can see what would happen here:

If the TPR valve starts to overflow and develops a constant drip, this is a sign that your overflow valve is malfunctioning. This can happen if a valve has weakened with age. It can also happen when deposits of minerals build up inside of the valve. Either way, your TPR valve should be checked annually and replaced when necessary. (Unless, that is, you want your water tank to explode) In this post, we’ll describe how to test your TPR valve and replace it.

Check the TPR Valve

To ensure it’s working well, your TPR valve should be checked on an annual basis. First, remove the the discharge pipe from the TPR valve. Once this is done, hold a bucket directly beneath the TPR valve and lift the valve gently to open it.

Drain one or two cups out of the hot water tank. Be careful! if you have your hot water tank set to scalding temperatures, you could burn yourself. Wear gloves while you do this and be gentle with the valve to prevent it from releasing an explosive blast of water.

If opening the valve releases no water from the tank, then your valve is clogged and must be replaced immediately. If the valve releases water from the tank but then begins to drip and won’t stop, this is another sign that the valve needs to be replaced.

Replacing the TPR Valve

  1. Turn off the cold water entering the tank.
  2. Turn off the power or the gas to the tank itself. Instructions for doing this will vary from one tank to the next. Check your owner’s manual if you’re not sure how it’s done.
  3. Turn on a hot water faucet somewhere in the house to a dribble to prevent a vacuum from forming inside your hot water tank.
  4. Hook up a hose to the spigot at the bottom of the tank and drain enough water that the level of the tank falls below the valve in the tank. If the valve is on the side of the tank, this should be about 5 gallons. If the valve is on top of the tank, empty one or two gallons.
  5. Buy a replacement valve that matches the exact temperature and pressure settings of your current valve.
  6. Use a pipe wrench to loosen the valve, turning it counter clockwise.
  7. Remove the old valve.
  8. Wrap plumber’s tape around the threaded section of the new valve.
  9. Use the pipe wrench to screw the new valve into the side of the tank.
  10. Turn on the cold water to the tank.
  11. Turn on the power or the gas when the tank fills with cold water.
  12. Turn off the faucet that you turned on in step 3.
  13. Test the valve as described above. If the valve is working and there are no leaks, your job is done.

That’s it! If you’re still not feeling comfortable with this process, take a look at this very helpful video:

Or call us at Terry’s Plumbing. We’ll replace the valve for you and check your water heater for signs of trouble. Contact us at (412) 364-9114.

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