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Thread: Relief Valve

  1. #1

    Default Relief Valve

    Hello, I'm a newbie to these boards and a newbie to plumbing.

    My 3 year old hot water heater starting "leaking" from the relief valve a few weeks ago. Not a continuous leak, but maybe once or twice a week I'll see a couple of tablespoons to a 1/2 pint of water in the tin I put underneath the valve.

    I've been told 2 things: either I need to replace the relief valve or I need an expansion tank. I was told to hook up a water pressure gauge with a lazy hand to the washing machine line to test the water pressure. I did this last night and it got up to 85 psi....but no water in the tin this time. What do you suggest? I heard that if it goes above 150 I need an expansion tank???

    Please help.
    Thank you in advance,
    Arthur.

  2. #2

    Default

    Lift the lever up and down several times. Maybe the stream of water will blow out sediment and reseat the valve properly.

  3. #3

    Default

    Be careful! The water coming out will be hot, of course.

  4. #4
    Plumber jimbo's Avatar
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    Actually, if it is over 75 continuously, your pressure reducing valve has failed. If it creeps up when the WH burner is operating, that is symptomatic of the need for an expansion tank. However, even in that case, the TP should not drip unless the pressure gets to about 125. If it drips at a lower pressure, it may just be that replacing the TP is all that is necessary.

  5. #5
    Plumber Deb's Avatar
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    Default Deb

    I am more of the opinion that it may be debris in the valve or most likely just time for a new valve. When excess pressure causes a T & P to open, it generally opens and releases a full flow--far more than 1/2 pint-- and closes when the excess pressure is reduced.
    Deb
    The Pipewench

  6. #6

    Default

    thank you for your insights. I have "Lifted the lever up and down several times"...but that didn't do the trick.

    It's now been 2 days with the gauge and the highest it's gone is 90....but no water from the relief valve. My assumption is that when the pressure gets to 100+ (maybe 120) the water leaks a half pint or so (or more)....so is that an expansion tank? I would think that if the relief valve is bad it would leak at 90?

  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    The pressure is always higher at night while everyone is sleeping.

    Nobody is using water and the water towers are filling, which adds to the pressure in the homes.

    Most codes require a pressure reducer if the water is over 80 pounds.
    If a reducer is added, an expansion tank is needed, the reducer "closes" the system, and the warming water has no place to go without the expansion tank.

    If you install an expansion tank, it "may" prevent the spillage from your prv valve. Yes, I would use the word "may".

    PRV valves come set for 150 PSI and 210 degrees when new.

  8. #8
    Plumber jimbo's Avatar
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    You still haven't told us what the "usual" pressure is..We understand that is sometimes gets up to 90 or so, but where is it when nothing is going on? Is it under 80?

  9. #9

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    it's usually at 40-45...then at night goes up to 90.

  10. #10
    Plumber jimbo's Avatar
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    I think you should replace the regulator. No matter what happens to the street pressure at night, your house side should not creep up like that, unless the creep is directly associated with operation of the WH. Then, it's expansion tank time.

  11. #11

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    I still haven't fixed this yet

    but yesterday I saw when this happens.

    After 2 baths went for my kids, the water leaked from the relief value into my pan. The water was cold. Can it be that we use a bunch of water at one time, then the water heater fills up the tank but since the relief valve is not "tight", then the water comes out a bit.

    Does that make sense?

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    No, what makes sense is that the more empty the hot water tank is, the more that needs to expand when all of that cold water finally heats up...time for an expansion tank.
    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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