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Water heater leaking through relief valve

14 years ago

Hi I have one of three electric water heaters that is leaking through it's T/P relief valve. I replaced the valve and the problem still exists. There has never been any expansion tanks on these water heaters since I bought the place so I am assuming the incoming presure reducing valve has a 'bypass feature'. What am I missing here? Should I just install a expansion tank? Thanks in advance.

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Comments (14)

baymee
14 years ago
If there's a check valve ahead of the heater, you'll probably have to install the expansion tank. Might be required anyway.
User
14 years ago
THERMAL EXPANSION... click here
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brickeyee
14 years ago
If a bypass is present it could very well be clogged.

Some can be cleared, others mean a new PRV.
User
14 years ago
Accommodating thermal expansion is not the job of a PRV. Some PRVs have a bypass and some don't. PRVs fail more often then you'd believe.

Your T&P burping is telling you to install an expansion tank and if you check your plumbing codes I believe they will also tell you to install an expansion tank.
brickeyee
14 years ago
"Accommodating thermal expansion is not the job of a PRV."

It is if the PRV has a bypass.
User
14 years ago
"It is if the PRV has a bypass".

And as I said "PRVs fail more often then you'd believe".

If the OP's PRV has a bypass it seems to have already failed. If the OP's PRV doesn't have a bypass then a thermal expansion tank is the best all around resolution.

A thermal expansion tank is prominently mentioned in numerous plumbing codes I've looked at and is easily checked for proper operation. I've never seen a bypass listed as required in closed plumbing systems but I may just be missing it.

You use the PRV with bypass in your house and I'll stick with the tried and true and simpler solution.
pscribner
Original Author
14 years ago
OK, thanks guys. Will add exp tanks as an additional safety precaution. What puzzles me still is why just this one water heater and not the others.They have the same feed. Maybe the temp setting is higher maybe?
brickeyee
14 years ago
The bypass prevent the creation of a closed system.

Thermal expansion tanks do not have a great history of longevity either, and create a 'dead end' in the potable water system.
User
14 years ago
"Thermal expansion tanks do not have a great history of longevity either, and create a 'dead end' in the potable water system".

There are far more posts on this forum regarding failed PRVs than failed expansion tanks.

Expansion tanks are easily checked for correct operation and easily replaced if necessary and without shutting off the water to the house IF they were installed properly with a shut-off valve.

Expansion tanks are no more of a dead end in the potable water system than an unused hose bib.

The expansion tank in my home was installed in 1995 and is still operating while in that same time period my PRV has been replaced three times.

With respect, I agree to disagree and as I said... "you use the PRV with bypass in your house and I'll stick with the tried and true and simpler solution".
lazypup
14 years ago
Per code, a "Dead end" is defined as a line longer than 12" that is capped. Given that few expansion tanks would exceed the 12" length they are not defined as a dead end.

In addition, contrary to the popular opinions of the people who frequent this forum, there is no prohibition against installing expansion stubs in place of manufactured expansion chambers.
alphonse
14 years ago
"What puzzles me still is why just this one water heater and not the others.They have the same feed. Maybe the temp setting is higher maybe?"

Describe how the heaters are piped- are they in series/parallel or remotely located. Describe location of TPR valves on the tanks, and whether they're OEM, specifically, trip stem length.

The tank in question would deliver scalding hot water and trip the Electric Cut Off if the temp setting was enough to thermally pop the TPR.
baymee
14 years ago
If one was to install an expansion stub, would it be vertical and less than 12"? And would more than one be necessary?
alphonse
14 years ago
For an expansion stub to function, there must be trapped air to compress so vertical orientation is req'd.
Longer length means a longer period for air entrainment.
Bladder tanks are a better solution but not necessarily indicated in the OP's case.
baymee
14 years ago
I ran into a local plumber this morning and he said a stub will not pass inspection and asked for the code that said it would.

Eventually the air in the stub would be absorbed into the system and cease to function.

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