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How to Replace a Temperature and Pressure (T&P) Relief Valve in a Water Heater

Updated on July 27, 2017
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Dan has been in the HVAC industry for 22 years with experience in aspects ranging from installation and service to sales and distribution.

The T&P Valve is There for Your Safety

Has your T&P valve stopped working properly? If so, be glad that you caught it before there was a more serious problem. The T&P valve is there to release pressure if the tank should overheat. Without this valve, or proper function of it, your tank could potentially explode. Now this is a worst case scenario but that is why the valve is there. With 15 years of experience with gas burning appliances, trust me when I say not to take safety risks with your gas appliances.

The good news is that you caught it, it's not expensive to fix and can be done rather easily.

There are a couple simple things we can do to check and see if our valve is working properly. If it's not, then the following will help you to obtain a new replacement valve, know how to install it and provide you a list of other items you will also need.

Checking Your T&P Valve

First, check and see if there is any water directly under the discharge line. This is the piping that is (should be) attached to the T&P valve. If you see water, either the valve is leaking or the temperature of your tank is too high. The discharge line directs the path of the water safely should the valve open. Without a discharge line, the water can spray in any direction and of course can be scalding hot.

  • If you turn down the temperature on your tank for a day or 2 and the water goes away, then you know you had your tank set too high. It is not recommended to have the water any higher than 125 degrees in temperature.
  • If the water is still there after you've turned down the heater, then it's quite likely the valve is leaking and you should replace it.

If there is no water on the floor, then test the T&P for being stuck shut. You can do this by lifting the lever on the valve just slightly enough to allow a small amount of water to be released and hear a bit of hissing. You may want to place a towel or bowl at the end of the discharge line to catch the small amount of water you're likely to release. Do not open the valve all the way or you could have a mess on your hands.

  • If this is what you hear, then your T&P is operating properly. Just push the lever back down and you're all set.
  • If there is no water release or hissing, your T&P may be stuck shut and you should replace it.

Things You May Need

Tools
Parts
Accessories
Pipe Wrenches
T&P Valve
Teflon Tape
Tubing Cutter or Hacksaw
Discharge Tube
Emery Cloth or Sandpaper
Pliers
Coupling
PVC Glue
Click thumbnail to view full-size
Pipe WrenchesTeflon TapeTubing CuttersHack SawCopper Discharge Line (3/4")Coupling (push fitting)Coupling (PVC)PVC GlueThere are a lot of different PVC glues available. For this task, just be sure the glue is good for use on PVC.Emery Cloth
Pipe Wrenches
Pipe Wrenches
Teflon Tape
Teflon Tape
Tubing Cutters
Tubing Cutters
Hack Saw
Hack Saw
Copper Discharge Line (3/4")
Copper Discharge Line (3/4")
Coupling (push fitting)
Coupling (push fitting)
Coupling (PVC)
Coupling (PVC)
PVC Glue
PVC Glue
There are a lot of different PVC glues available. For this task, just be sure the glue is good for use on PVC.
There are a lot of different PVC glues available. For this task, just be sure the glue is good for use on PVC.
Emery Cloth
Emery Cloth

How to Find a New T&P Valve

The T&P valve should have a tag on the top of it attached to the handle. The information located on this tag is what you'll need to find the proper replacement. Do not substitute your valve with one that is rated differently as this can cause a whole new problem.

Most hardware and home improvement stores carry replacement valves but if yours does not, try a local contractor or contractor supply house. Typically supply houses deal with contractors only, but some will sell this part to a private homeowner.

This is an example of a top mounted T&P valve.
This is an example of a top mounted T&P valve.
This is an example of a side mounted T&P valve. Notice there is no discharge line. A new tank does not come with the discharge line and must be purchased separately.
This is an example of a side mounted T&P valve. Notice there is no discharge line. A new tank does not come with the discharge line and must be purchased separately.

How mechanically inclined are you?

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Replacing the Valve

Replacing the T&P valve is not a difficult task but we do want to make sure we are safe. I personally suggest you drain off the tank completely before performing this task. Not only will this help to eliminate possible messes and accidents, it should be done yearly and it's likely you are due to perform this maintenance.

Now that the tank is drained, open the valve all the way to make sure all pressure is released from the tank and proceed to disconnect the discharge line. It's possible that you are lucky enough to have a valve on the side of your tank or be able to unscrew this line in it's entirety because you have the ceiling height to do so. However, many of us will have our valve on top and not have the ceiling height to allow this. The tube will hit the ceiling if we try to unscrew it in one piece so we will have to cut it with our tubing cutter or hacksaw. Be sure to put on wrench on the discharge and one wrench or pliers on the valve to apply opposing pressure. This will help avoid too much pressure on the valve in which it can deform the top of the tank or the hole it is in if the discharge is screwed on very tightly.

If you are able to make a clean straight cut on your discharge tube, save it. You will be able to put it back together with a coupling and not have to buy a new discharge line.

Now with the discharge line off of the valve, we should be able to unscrew the T&P valve from the tank with our pipe wrench. If the valve is tough to unscrew, try tapping the end of your pipe wrench with a hammer or putting a pipe over the handle of your wrench to extend it. This will give you extra leverage if you need it. Do not force the issue. If you're putting your foot on the wall and yanking on the valve too hard, you could possibly damage something. Especially with the tank empty as it will be lighter and you could twist the tank and all that is attached to it. This would be very bad.

With the old valve off, we should now get our new valve and wrap the end that we will be screwing back into the tank with our teflon tape. Be sure to wrap the tape in the opposite direction that you will be screwing the valve in; your tape will unwrap if you don't.

Once you've wrapped the valve threads a few times, screw the new valve into the tank. You'll want to tighten it down good while making sure the valve ends up in position to reattach the discharge line.

Reattaching the discharge line will also require teflon tape to be applied to the male threads before screwing it into the T&P valve. If you had to cut your line, "couple" it back together once you've screwed in the first piece. If your line is PVC, you'll want to purchase a PVC coupling and PVC glue, to put it back together. Simply apply the glue to the pipe end and inner coupling and push it onto the pipe. If your discharge is copper, I suggest buying a "push fitting" coupling to put it back together. The push fitting is great because you just push it onto the pipe until it clicks into place. There is no soldering or special tools required. Just sand the two ends of your pipe a bit to remove any burrs or build up for a good fit of the coupling.

It's likely your discharge is 3/4" in diameter but take a piece of your discharge to the store with you to be sure your coupling will fit.

Replacing the temperature and pressure relief valve on your tank is done. Check that your pilot is still lit and that the tank fires back up as it should Now you can refill the tank and check your new valve for leaks and proper operation.

Another Job Well Done!

I know it's been a busy day, draining the tank, going to the hardware store, doing the job...but now that it's done, you can sleep a bit easier with the tank operating safely. Give yourself a pat on the back and enjoy your evening. You deserve it.

As always, if you experience any difficulty or problems with your water heater, contact a professional for assistance. Never make assumptions when dealing with a gas burning appliance.

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    • Cre8tor profile image
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      Dan Robbins 5 years ago from Ohio

      smithdave - You're welcome and thank you for reading.

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      smithdave 5 years ago

      Thanks....