TP valve problem

[Gary Swart]

My 12 year old TP valve was dripping. Not a stream, but a fairly constant drip. I replaced it. The new valve seemed fine at first, but a few hours later I discovered it was dripping. I opened it several times but it would not seal. In fact, at times it was running in a stream. Assumed a bad valve. Returned it and got another new one. Installed it and I have the same problem. This hot water system has been exactly like it is for 9 years and has not caused me any problems. I have tested the water temp and it is 120 degress. There is no expansion tank, but there never has been one. I doubt that I would get 2 defective TP valves, so I'm seeking other possibilities.

 

[Jadnashua]

Buy a pressure gauge and check it out. The city/town may have changed a pump, and the pressure may be higher or they redid some supply mains, or something else that changed the conditions. It could be that three TP valves are bad, but it is not likely. They may just be doing their job. If you have a prv, it may have failed, letting the pressure rise, too.

 

[Sponsor]

 

[Gary Swart]

Already had a pressure gauge so per your suggestion, I checked the pressure. I have 76 psi. That's about what it always has been. I know it's a tad higher than the recommended pressure so if that's the problem, I can easily install a PRV. Fortunately, my water heater sets on a shelf that is inside a mop basin with a floor drain so I'm not having a flooding problem. Thanks for the opinion, maybe someone will have something else to check out.

 

[Cass]

was the water coming out of the T&P when you checked the pressure? Leave the pressure gauge on the faucet and check it when the water is coming out of the T&P.

 

[Gary Swart]

No, at the moment I check the pressure, there was nothing coming out. I'll try your suggestion. I set a plastic bowl under the pipe about 2 hours ago, and when I checked it just now, there was about 1" of water in the bottom. That's far less than has been leaking, but it's still not right of course.

 

[Jadnashua]

Sounds like something is spiking your water pressure. It may be time for a prv and and expansion tank. You'll know if you can see if the pressure rises, but my guess is you should go that route. Have you had your water meter replaced recently? Some of them have check valves in them...use of hot water, and the subsequent expansion of the cold water that goes into the tank can give the symptom you are having.

 

[Gary Swart]

Jim, I think you've hit the nail on the head! I put my pressure gauge on the line and left it all evening while I did some other work. I check it now and then and it was hold 76 psi. The just as I was quitting for the evening, I was at the gauge when the heat kick on (gas) I looked at the gauge and about crapped! The gauge goes to 100 psi and it was pegged way past that. My meter is 22 years old, I had a new 1" installed when I put in my sprinkler system. Interesting, there doesn't seem to be any leakage at this time. I'll check the bowl in the AM and see what happens overnight. I will also make a trip to the plumbing shop and get an expansion tank and PRV. Hopefully those will cure the problem. Mega thanks to you and to Cass for you helpful advice.

 

[Gary Swart]

Forgot to add that when I saw the psi so high, I opened a faucet for a few seconds and the pressure dropped to normal. I had also check the pressure on the cold water supply when the hot was so high and found it to be still at 76.

 

[aurelio alarcon]

Exchange the valve before doing anything else. That's what I would do. But you might find another solution. Best of luck!

 

[Gary Swart]

Did that already, same result. I'm sure the expansion tank will cure the problem. It will install it on Friday as I have to be out of town early tomorrow afternoon and I don't want to be in the middle of the job and have to stop. In theory it's a simple enough job, but in the real world, there always are the unforseen things like not having a fitting or a space problem to be solved. I'll gopher parts tomorrow and lay everything out so Friday should be a piece of cake. Thanks for the suggestion.

 

[hj]

psi

If the pressure increases while the water heater is operating, then the expansion tank will cure it. If the pressure "creeps" up over time, which your description seems to indicate is not the problem, then you would need to replace a pressure regulating valve somewhere that is going bad.

 

[Gary Swart]

Just want to report that I finished the installation of a PRV and expansion tank, and the operation appears to be highly successful! The pressure gauge stays right on 50 psi when the heater is in operation. I'm quite sure there will be no trace of water from the TP valve when I check it in the morning. We will have to adjust to lower pressure than we have been accustomed to, it was 76 psi, but we're tough and can probably adapt to sure primitive conditions in time. Thank again to all who chipped in with advice. Most everyone was right on with their comments.

 

[hj]

prv

You do not have to "adjust to the lower pressure". I typically adjust the PRV's I install up to the 70 psi level.

 

[Cass]

PRVs typicaly come preset to 50#

 

[Master Plumber Mark]

12 year old heater??

did you think to change out that 12 yr old heater too while you
were at it???

I have found that the T-stat sometimes over heats the
system which makes the pressure spike like that........

wait and see what transpires, I guess


just wondering...

 

[Gary Swart]

I was wrong about the age of the heater. It's just 9 years old. Thanks for the concern.