Dan has been in the HVAC industry for 23 years with experience ranging from installation and service to sales and distribution.
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 it 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 two 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
Tubing Cutter or Hacksaw
Emery Cloth or Sandpaper
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. Supply houses typically deal with contractors only, but some will sell this part to a private homeowner.
I like a universal valve that will work on a majority of water heaters out there. I use this one quite frequently and have installed this little guy more than I care to count. It's a quality made and reliable pressure relief valve.
Replacing the Valve
Replacing the T&P valve is not a difficult task, but we do want to make sure we are safe. So let's get started!
Step 1: Drain the Tank (Optional)
I personally suggest you drain off the tank completely before performing this task. Not only will this help to eliminate possible messes and accidents, but it should also be done yearly. It's likely you are due to perform this maintenance.
Step 2: Disconnect the Discharge Line
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're lucky enough to have a valve on the side of your tank or be able to unscrew this line in its 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 if that's the case for you, you'll have to cut it with a 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.
Step 3: Unscrew the T&P Valve
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.
Step 4: Screw in the New Valve
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.
Step 5: 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.
- PVC Lines: 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.
- Copper Lines: 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.
UPDATE: There's a new solution available to reattaching the discharge line that's pretty great. It's called a SharkBite fitting. It will allow you to attach either PVC pipe or copper piping to your T&P valve with no soldering or gluing! You just press it in firmly, and it seals up tight. This 3/4-inch SharkBite fitting is the one you'll need (if you have 3/4 inch piping—which all most all are). I use these all the time now and have yet to have one leak. Isn't technology grand?!
Step 6: Final Checks and Tests
Replacing the temperature and pressure relief valve on your tank is basically done! There are just a few last steps you'll want to do to make sure everything is working as it should be.
- 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. Once your tank is filled, try opening the T&P valve by flipping up the little silver handle on top of it very briefly. You should be able to hear the hiss of water flowing out. Make sure it's closed when you are done with your test.
- Lastly, give everything a once over and make sure there aren't any leaks.
Good job! That's it, you're done!
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.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2012 Dan Reed
billjones on July 03, 2018:
Thanks, I fill more comfortable in doing the repair.
Dan Reed (author) on June 26, 2012:
smithdave - You're welcome and thank you for reading.
smithdave on June 26, 2012: