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Thread: leaking temp/relief valve

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  1. #1
    DIY Member trw888's Avatar
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    Default leaking temp/relief valve

    Hi,

    I did a search for the problem I'm having and I'm pretty sure I've found the problem. But I just want to confirm that I'm correct.

    I've got a Bradford While 40 gallon gas water heater. It was installed in May 2010 by a pro. Today, I opened up the water heater closet door to find the floor was quite wet and water dripping every few seconds from the copper pipe that extends down the side of the tank. Am I right that it's the temperature pressure relief valve that the pipe is connected to and that this valve has gone bad?

    Seems hard to believe it would go bad on such a new tank...

    Thanks, Tim

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    DIY Member trw888's Avatar
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    I forgot to add -- in case these things matter -- that the water coming out of the pipe is cold. There's no difference in water pressure nor lack of hot water inside the house. And we have a Watts recirculating pump on the heater

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    DIYer, not in the trades LLigetfa's Avatar
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    If you have a checkvalve in your system and no expansion tank, it could well be the TPR valve is doing exactly what it's supposed to. Open a tap just enough to sustain a drip and see if the TPR valve stops relieving.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    A T&P valve will open for three reasons: the water temperature exceeds it's safety limit (not your problem, if your water isn't excessively hot), the pressure excees it's safety limits (possible), or, it is worn out or defective. Sometimes, mineral deposits can prevent the valve from closing if it was opened in the past for a valid reason.

    So, the recirculation system won't raise the pressure enough (if at all) to open the valve. BUt, it could cause the WH to run more often, and if you do have a closed system (like mentioned), then if you don't have a working expansion tank, the pressure is too high. Water doesn't compress, and when heated, expands. If there's no place for it to go, the pressure rises dramatically, until something gives. This is often the T&P valve. Sometimes, it's a toilet fill valve, or maybe the washing machine hoses, or faucet hoses, or maybe hammer arresters, but that now 'bigger' water needs somewhere to go. The solution is an expansion tank, normally, unless the valve is bad.

    If it's only a few drops, over the length of the pipe, it could cool off, unless the flow was fairly high.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member trw888's Avatar
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    Thanks for the replies. I tried the drip test. Maybe I didn't let it drip long enough, but it didn't appear to make any difference. I should note as well that a roughly 2' X 5' area of the floor in the water heater closet is quite saturated. I know for sure the dripping started no more than a week ago so it's dripped a fair amount of water. It sounds like an expansion tank is in order. Any thoughts on why this would happen all of a sudden? We've never had a problem like this before.

    Thanks again.

  6. #6
    DIYer, not in the trades LLigetfa's Avatar
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    How much the expansion will spike the pressure will depend on several factors. The more hot water you use at once, the more there is to heat and expand. Any water use over the course of time can bleed off some of the expansion. That was what I was attempting by leaving a faucet dripping. The water use can be an automatic humidifier on a furnace, an ice maker, etc. If the humidistat has not called for the furnace humidifier, and/or ice making or other uses are sporadic, there is opportunity for the pressure to spike.

    Then again, it could be as Jim said, namely that there was a valid reason at one time for the TPR valve to relieve and it has not reseated. It is also possible that it has had a very tiny leak all along and built up with corrosion and mineral that has since pushed it further open.

    I am on a well system with an expansion tank so my old tank had no valid reason to ever pressure relieve but when we were pulling the tank, I tried to trip the TPR valve to let air in so it would drain faster, only to be surprised that it was frozen shut from corrosion and mineral buildup.

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