Thermal Expansion Tank Failure?

Hello. I'm brand new to the forum here and by the looks of the good advice being given out here - I could have used this a long time ago. I'm an accomplished DIY'er and know my way around plumbing a bit (not a pro but my local inspector likes my work). I'm located in Los Angeles and my set up is as follows:

- 50 Gallon G.E. gas water heater (2 years old) temp set to 125 degrees.
- Watts PLT-5 Expansion tank (2 years old) installed just after the hot water heater tank shut off and with a pressure gauge just before the expansion tank.
- Wilkins 600 series PRV. (Making a closed system). Pre-valve pressure is 180 psi. Post valve pressure is 60 psi.
- Wilkins PTV valve right after PRV (before it enters the crawl space).

My questions are:

My PTV valve started leaking recently I tried a new valve (still leaks). Then I tried recharging and reinstalling the expansion tank but I'm still getting a leak. How likely is it that the expansion tank has failed after just 2 years? If it has how can I be sure it's dead and that it's the cause of my leaking PTV valve?

Any info is greatly appreciated. I can provide a pic in necessary.

Thanks,

Solan

who knows ...

Install anew t+p valve on theheater and see if the problem just goes away....

sometimes they just go bad for no reason...

my opinioin on the thremal tanks is they
ought to be set at about 10-15 lbs higher than your
water pressure at the prv

of course that is up for debate. too..


sorry, i did not read the whole post...

you probably have too high a pressure comming
through the prv valve

tank

IF water does not come out of the air fill valve on the tank, AND it has air pressure when the tank is drained or removed from the system, then it is still functional to some degree. The amount of air will determine the degree of functionality. What does you pressure gauge say while all this is going on? You could have a bad PRV, not a bad expansion tank.

what does the pressure gage say?

The gauge has a peak pressure indicator that shows 150psi (just since last night) but after opening a hot water fixture it levels off at 60 psi. I've included a shot of the tank as installed.

If I read it right, you installed the expansion tank on the outlet of the WH? That will decrease its life considerably...it should be on the inlet to the WH.

With a pressure spiking to 150 PSI a new T&P valve will also open... At least if it is not defective. Now all you have to do is figure out if the PRV is defective allowing the pressure to spike to 150 PSI. Or, if the expansion tank is failing to absorb the thermal expansion.

Thermal Expansion drama continues

Thanks for the replies everyone.

Jadnashua, the expansion tank is on the supply side of the water heater (I wasn't clear on that). I installed the tank just after the inlet ball valve.

Redwood, how can I test the tank or the PRV? It has to be one or the other...doesn't it?

Lastly, is the 150 PSI a "normal" expansion pressure for a set up like mine or does that seem outrageous?

Any insight will be greatly appreciated.

Thanks in advance.

-Solan

With the water heater not heating run a small amount of water the shut it off and watch the gage. It should remain steady at the set point without creeping up.

Then run a large amount of hot water so the water heater a heating a large volume of water and watch the gage. As the water heats you will probably see a large rise in pressure. This would be the pressure induced by thermal expansion.

There is a air valve on the expansion tank. Press in the valve and see if water comes out. If it does the bladder is comprimised and the tank needs replacement. If water does not come out the precharge may be incorrect. Shut off the water and bleed the water system pressure down. Use a bicycle pump to set the precharge to the water system pressure.

http://www.watts.com/pdf/1915356.pdf

PRV is the culprit

Well I think I've found my problem: the PRV. I actually shut off the water heater for a few hours and the pressure kept creeping up (after about 2 hours it was at 120 PSI and rising. I'm considering rebuilding the PRV. It's a Wilkins Model 600. The new valve will set me back approx. $100. The rebuild kit is approx. $45.

My question: Is it worth rebuilding? (The PRV is 6 - 7 years old).

Thanks in advance.

-Solan

Replace it! You are sure that the creeping up was not caused by the water heater heating?

Prv

Do not waste your time and money rebuilding it.

Solan said:

Well I think I've found my problem: the PRV. I actually shut off the water heater for a few hours and the pressure kept creeping up (after about 2 hours it was at 120 PSI and rising. I'm considering rebuilding the PRV. It's a Wilkins Model 600. The new valve will set me back approx. $100. The rebuild kit is approx. $45.

My question: Is it worth rebuilding? (The PRV is 6 - 7 years old).

Thanks in advance.

-Solan

Click to expand...

Grainger is having a clearance sale on discontinued 1" Watts N35BU valve for $15.70.
http://www.grainger.com/Grainger/items/6LM11

Pressure problem fixed!

Thanks to everyone who took the time to reply to my original post. I installed a new PRV (Wilkins 600) and the problem was solved. The pressure has been sitting pretty at 60 PSI all day.

Thanks again,

- Solan

Congratulations on the "Correct" diagnosis!