Temp & Pressure Valve Replacement Advice Needed

[sstauffer7]

Hey all,

First time poster here. I've noticed my temp and pressure valve leaking hot water after I replaced the elements and thermostats in my AO Smith water heater. I am wondering, what would be the best way to go about replacing this. It looks like a simple cut the copper tubing, replace the valve and re-sweat it back together... My only problem is I've never sweat piping. I get the gist of how to do it, but don't understand where I would cut/replace add cupplers, etc... Any advice to keep this simple as possible would be greatly appreciated!

Thanks in advance.

 

[jeffmattero76]

First, are you sure you don't have the temperature set too high? It should be set to around 120 degrees.

Second, have you checked the water pressure. You can buy a pressure gauge at one of the big box stores for about $10. Just screw it to a hose bibb to measure. Should be less than 80 psi, usually best around 50 psi.

Assuming both of those are set correctly, changing the T&P valve is pretty simple, but I would need to see a better picture to help. Where does that copper pipe go? Take a picture from farther back to show all of the copper pipe.

Typically, the T&P valve simply screws into the tank, and there is a tube that screws into the T&P valve that goes straight down to the floor and ends about 4 or 6 inches above the floor. The big box stores sell these tubes in PVC with a steel male threaded end for a couple of dollars.

To change the T&P valve, you would turn off the incoming water, and open a faucet to let in air, and then drain some water out of the valve at the bottom of the water heater. You need to get the water level in the tank to be lower than the opening for the T&P valve.

 

[sstauffer7]

Awesome. Thanks for your reply. I will plan on testing the pressure before doing anything. And yeah, I’ve got the thermostats set to 120 when I installed new ones a couple weeks ago.

The T&P drain goes through my exterior wall out to my backyard. That’d actually where I noticed the valve was failing, it was dripping. So the first thing I did was tested the valve by opening and closing it, and after doing that it seemed like it would close back all the way.
Here’s a pic.

 

[jeffmattero76]

If you don't want to solder, you can fix it using sharkbites and pex.

You would cut the pipe about 1 inch to the right of the first ell (the one closest to the T&P valve), and cut the pipe again about 3 or 4 inches above the third ell (the one that turns the pipe to go outside). Use a pipe cutter for those cuts.

Using a pair of pliers on the shoulder of the fitting, remove that stub of copper that is connected to the T&P valve and set it aside (you will need to reuse it). Remove the bad valve (after draining the water down a little below the valve opening).

Then, in addition to the new T&P valve, buy 2 sharkbite couplings, and a sharkbite 90 ell. Also buy a 10 foot stick of pex ( they come in 10 foot lengths as well as 50 foot rolls). I would use white pex if it were my house.

Push one sharkbite coupling on each of the copper pipe ends. Install the new valve, using pipe dope or teflon tape on the threads. Then, screw the stub of copper that you set aside earlier into the valve. Then cut lengths of pex the same lengths as the pipe you removed, and insert the sharkbite 90 ell between them. Push each end of the pex into the couplings on the copper stubs that you left.

Let us know how you make out.

 

[sstauffer7]

Okay great, thanks for the help! One other question as I begin to do this... I’ve noticed the model Cash Acme NCLX - 5L on my valve... I could order the exact one online but Home Depot has the NCLX - 5LX... it appears to have the same spec ratings, just a little bit longer threaded shaft. Any harm if I throw that one in instead?

 

[Diehard]

Is it a constant dripping. i.e. - Never stops dripping?
Did you try lifting the relief handle a couple of times to blow out some water? Just in case it got some foreign matter in there.

 

[sstauffer7]

Is it a constant dripping. i.e. - Never stops dripping?
Did you try lifting the relief handle a couple of times to blow out some water? Just in case it got some foreign matter in there.

Yeah, in fact after I did that it felt like it would not close all the way. I got it out and it’s got all kinds of deposits on it. Just wondering if I need the exact replacement part or if i can substitute it with a similar one with the same ratings?

 

[Diehard]

I would assume that the, "little bit longer threaded shaft" just gets probe a bit further into the tank for those tanks that may have thicker insulation.
I would think that as long as neither pipe entering the tank are in the way of the probe, it would be okay.

 

[jeffmattero76]

I agree with Diehard, but I am not a plumber.

 

[RenewDave]

You don’t have a thermal expansion tank on your HWH. The T&P May be doing its job and your issue may be thermal expansion. And, we cannot use pex as piping for a T&P valve. Check your codes.

 

[Diehard]

Yes I was going to ask if you had an expansion tank and/or any type of backflow prevention device on your water service. As that is sometimes the problem.
However, I assumed(which I don't like to do) that if it was a "constant drip" rather than an occasional release, as would be caused from over pressurizing, that it was in fact a fouled T&P valve in need of replacement.

 

[frodo]

Hey all,

First time poster here. I've noticed my temp and pressure valve leaking hot water after I replaced the elements and thermostats in my AO Smith water heater. I am wondering, what would be the best way to go about replacing this. It looks like a simple cut the copper tubing, replace the valve and re-sweat it back together... My only problem is I've never sweat piping. I get the gist of how to do it, but don't understand where I would cut/replace add cupplers, etc... Any advice to keep this simple as possible would be greatly appreciated!

Thanks in advance.

1]
when you changed the element did you open the pop off [T&P] valve to bleed the water heater?
have you ever opened the T&P valve
2]
because you said you replaced the t stat and elements
I would look at the temp setting of the t stat...verify that the element you installed matches the wattage of the one you removed.
after those items have been looked at and verified, we can move on to other options

 

[frodo]

Yeah, in fact after I did that it felt like it would not close all the way. I got it out and it’s got all kinds of deposits on it. Just wondering if I need the exact replacement part or if i can substitute it with a similar one with the same ratings?

just saw this
that is the problem

 

[FishScreener]

You don’t have a thermal expansion tank on your HWH. The T&P May be doing its job and your issue may be thermal expansion. And, we cannot use pex as piping for a T&P valve. Check your codes.

What code? The IRC, and IPC both allow any pipe approved for hot water. That includes PEX. But you can’t reduce to smaller than the valve ID, which means no PEX fittings.