Disagreement With Plumber

[Michael Stone]

A while ago we had our pressure reducer valve replaced because the plumber thought it was old and probably needed to be replaced (we weren't actually having any problems with it). I think it was a while after that we noticed that the TPR valve on the water heater was leaking a tiny bit. At the time we didn't think of the fact that the two things could be related.

So we had the plumber come out and replace the TPR valve (he said he checked the pressure as well and it seemed okay). Since he replaced the TPR valve it has been leaking a lot more, maybe a few cups a day. My thought is that since we had the pressure reducer replaced, when the water heats up now it can't flow back to the city so pressure is building up and being released through the TPR.

So I figured we probably need an expansion tank to take this excess pressure. The plumber disagrees, he think something else must be causing the problem. One thought he had was that the water might be too hot, but it seems to be about 124 degrees, which I think is okay (just a bit over the 120 recommendation). What do you think is likely to be causing this problem? Would an expansion tank be a good idea?

 

[Stuff]

Find a new plumber that has some common sense. Most codes require an expansion tank if you have a pressure regulator for the exact problems that you are having.

 

[Sponsor]

 

[hj]

If he replaced the PRV because it was "OLD", that might be your first clue as to his competency.

 

[Master Plumber Mark]

your plumber does not know his ass from a hole in the ground...

he should have installed that thermal expansion tank when he installed the
new pressure relief valve.....

 

[Michael Stone]

He came back today, and determined that the replacement pressure relief valve was bad (almost 2 years old at this point). He came to that conclusion because he said he measured the temperature & pressure at the water heater: 140+ degrees - too hot; 100 psi - too high. I had previously measured 124 degrees at the utility room sink, which is nearby. So he replaced the PRV again.
I made him install an expansion tank too. I had to ask him to strap it to the ceiling. We probably won't use his services in the future.
Total $200.
Thanks for the advice everyone!

 

[Stuff]

Silly question: Did he remember to charge the tank before installing?

 

[Michael Stone]

Silly question: Did he remember to charge the tank before installing?

You know, I'm a little worried about that. But I have no idea how to tell. I tried tapping on it, but I don't really know what it's supposed to sound like.

 

[Master Plumber Mark]

just put an air guage on the inlet and it should read about 80psi if he charged it ...
it will read only about 40 if he did not.

 

[Reach4]

just put an air guage on the inlet and it should read about 80psi if he charged it ...
it will read only about 40 if he did not.

While the water pressure is zero....

 

[Jadnashua]

The air bladder in the tank, when there is water pressure on the inlet side, will be exactly the same as your water pressure - open a water valve, then close it then check the pressure on the tank. Then, you need to shut off the water and open a faucet to relieve the water pressure (leave it open while you do the rest). THen, use a tire pressure gauge to check the air pressure again. It should be about the same pressure as you measured the first time. IF not, add air with a bicycle pump (you can do it with a compressor, but because the tank is small, it's easy to over pressure things). Then, you can close the valve you opened and turn the water back on. If the expansion tank was sized properly, you should be fine until it eventually fails, which could be a number of years. Make sure to reinstall the cap on the air valve...it acts like a secondary air seal to help prevent the tank from losing air though the stem.

Any time you have a closed water supply system ( a PRV makes things a closed system), when the water is heated after using some, that cold water expands, and since the pipes won't expand, the pressure spikes and the T&P valve SHOULD open. When you add an ET, the trapped air in the bladder can be compressed, barely rising the pressure in the system, maintaining the overall system pressure, preventing the T&P valve from opening (unless there's a failure somewhere).

 

[Michael Stone]

Good news, at least he did properly charge the expansion tank. I checked it with a bike pump (with pressure gauge) as suggested. Thanks again for all the help everyone.