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I installed a brand new water heater about 4 months ago, noticed that that relief valve was dripping like crazy. Checked the expansion tank and it was filled with water. I replaced it with a brand new expansion tank only a few months old. It was properly installed, got an accurate reading for water pressure from the city, set the air in the tank to a few pounds under that according to instructions.

Problem was fixed, the relief valve stopped dripping altogether for at least a month. This recently started back up however and right in the middle of a home inspection no less (I am currently selling the home). The home inspector included in his report that I have a faulty safety relief valve on my water heater and it needs to be replaced. The buyers in turn demanded that I replace the safety relief valve despite the fact that I am not even sure if that is the problem.

I even explained to the home inspector and buyers when they were there that the water heater and expansion tank are brand new. In your opinion is this a problem with the relief valve or the expansion tank or both? Is it normal to buy a new water heater with a faulty relief valve? Is it normal for a brand new expansion tank to already be taking on water?

EDIT:

I last measured this a few months ago, after opening faucet and releasing pressure from the water heater I got 30 psi. The water heater temperature is between HOT and A, but the knob goes all the way up to C. I filled up my NEW expansion tank to 28 psi and the dripping stopped completely for over a month. My father in law seems to think that calcium can buildup around the relief valve and cause this dripping I am seeing and that it is more likely to be a problem with the relief valve than the brand new tank.

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We still need your pressure and temperature readings from this question –  BMitch Oct 31 '12 at 13:40
    
There is a certain percentage of all new products that are faulty and slip through QA. Is it normal? No, but it does occur with all types of products –  Steven Oct 31 '12 at 13:42
    
@BMitch See my edits for the last readings I did. I suppose it would help if I actually get a current reading when I get home –  maple_shaft Oct 31 '12 at 13:48
    
What is the pressure on the cold water inlet? Do you have a pressure reducing valve (PRV) on the inlet? –  Tester101 Oct 31 '12 at 14:14
    
Tester may be right - the city pressure could be fluctuating from normal to high and the only way to even that out is to have a PRV for the whole house. It is a cheap part to rule that problem out. –  Bob A. Nov 1 '12 at 17:59
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2 Answers

The expansion tank needs to be charged with an air pressure equal to your system water pressure. Normally, this pressure is in the 50-60 PSI range. Too low of a pre-charge will cause premature bladder failure and also will cause the tank to not do its duty as an expansion tank.

The problem could also be a failure of the pressure relief valve.

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up vote 1 down vote accepted

Well the problem was simple enough. The expansion tank I installed that was only a few months old was completely filled with water. I guess 28 psi is too much for a pressure tank that was tested and verified for up to 100psi.

Now where did I put that warranty card? :)

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Careful, sometimes warranties are void if not installed by a professional. Read the fine print carefully before you call, or you might be disappointed. –  Tester101 Nov 1 '12 at 16:20
    
@Tester101 It wouldn't be the first time. –  maple_shaft Nov 1 '12 at 17:09
    
I think that the expansion tank needs to be charged to slightly above the system water pressure (normally around 50-60 PSI). When undercharged, it can cause the bladder to fail and also it will not do its job (causing the PRV to expel water). –  Pigrew Jan 30 '13 at 8:53
    
@maple_shaft, please accept your answer so that "community" stops bumping your question for attention. Thanks. –  BMitch Jun 29 '13 at 11:17
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