Relief Valve

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by arthur, Oct 28, 2004.

  1. arthur

    arthur New Member

    Messages:
    4
    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. Bob's HandyGuy

    Bob's HandyGuy Senior Member

    Messages:
    131
    Lift the lever up and down several times. Maybe the stream of water will blow out sediment and reseat the valve properly.
  3. Bob's HandyGuy

    Bob's HandyGuy Senior Member

    Messages:
    131
    Be careful! The water coming out will be hot, of course.
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. Deb

    Deb Plumber

    Messages:
    200
    Location:
    Idaho
    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. arthur

    arthur New Member

    Messages:
    4
    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. Terry

    Terry Administrator Staff Member

    Messages:
    15,003
    Location:
    Bothell, Washington
    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. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. arthur

    arthur New Member

    Messages:
    4
    it's usually at 40-45...then at night goes up to 90.
  10. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. arthur

    arthur New Member

    Messages:
    4
    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,003
    Location:
    New England
    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.
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