relief valve

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by MikeGr, Nov 18, 2005.

  1. MikeGr

    MikeGr New Member

    Messages:
    2
    This is a great forum, thank you Terry for setting it up.


    This is my issue.
    The pressure relief valve connected to my hot water heating system is
    opening more often than in previous years. The valve is doing its job, in
    that, the pressure remains at 30 after the furnace kicks in. From reading previous posts, I think maybe the valve needs to be replaced. My question is, is it OK to live with it for now, since I don't mind the inconvenience of dumping a pail of water occasionally? Are there any dangers that I should
    be aware of?

    Thanks in advance.

    Mike G.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,267
    Location:
    Cave Creek, Arizona
    valve

    Why would you want to change a valve that seems to be operating perfectly. Maybe you should check to see why the pressure is increasing when it should not. Such as a waterlogged or defective expansion tank.
  3. MikeGr

    MikeGr New Member

    Messages:
    2
    Good point. Would opening the relief valve for a bit drain the expansion tank?

    Mike
  4. plumber1

    plumber1 Plumber

    Messages:
    1,423
    Location:
    Florida
    valve

    Shouldn't use the relief valve as a drain valve.

    Pressure reducing valve could be leaking through or some one may have changed the adjustment.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,267
    Location:
    Cave Creek, Arizona
    tank

    No. Draining the expansion tank, if it is not a diaphragm type with a ruptured bellows, requires a precise routine to be sure all the excess water is removed and the proper air quantity is in place.
  6. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    I had two problems that contributed to overpressure. Waterlogged tank and failing controller.

    After discussion with installer of boiler I did the following to clear the tank.
    Shut off the makeup water valve. Open a drain in the water circuit on the boiler a little bit. It is usually somwhere near the boiler. Then add air to the bladder tank (Schrader valve like on your tires) to about 5 psi and leave the drain open until it stops flowing. Close the drain immediately when it stops flowing so you don't get air in the circuit. Check the pressure again and increase to about 5 psi. This was for a house with only one level above the boiler. You should see the tank pressure on the boiler gauge.

    Now open the makeup valve and you should see pressure equal to the regulator setting. Mine was about 10 psi.

    You should be able to run the furnace without the pressure gauge going into the red zone. Also check the temperature gauge. It shouldn't get above about 200 degrees, and that is probably on the high side.

    I had a problem where the temperature controller was not shutting off until the temperature was well above the setting. It was getting up to about 220 F. There were locally high temperatures that were causing steam to flash and collapse in the boiler and it was making an awful racket transmitted through the fin tubing. I had to replace the controller.
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