HW Heater Pressure Relief Valve- relieving

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by lee polowczuk, Dec 17, 2007.

  1. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    I have a gas hot water heater in my basement.

    I have been in the house for two years. The hot water heater is probably 5-7 years old.

    In the past three months or so, the pressure relief valve has released water 4 times.

    Recently, I turned the temperature down a bit, but it just took another dump the other day.

    There were no other problems with it the first couple of years.

    I have city water.

    Hot water in the house seems fine. 3 of us share two bathrooms. We probably use 7k gallons a month.

    The pressure relieve valve is screwed into the top of the heater with copper running across and then down to within a couple of inches of the floor.

    Any thoughts?
  2. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    PRV gone bad t&p bad do you have an expansion tank on your w/h?
  3. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    There is no expansion tank. I don't think i have ever owned a house with a WH expansion tank.

    The tag says 100xl extension 4 on the PRV...

    looks like it just screws in.
    Last edited: Dec 17, 2007
  4. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    Your PRV mayby malfunctioning,you need yo check your incoming water pressure.Try to find a pressure gauge to attach to a hose faucet laundry tray.
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,349
    Location:
    Yakima WA
    If you have a PRV, first make sure it is functioning. Buy a cheap pressure gauge that you can connect into the system. Any water system with a PRV should also have an expansion tank, and here's why. When water heats, it expands and must go somewhere. If a system does NOT have a PRV it is referred to as an "open system". In an opens system, this expansion is absorbed by the city water main, so no big deal. A system with a PRV is referred to as a "closed system" , This is because the PRV acts as a check valve and prevents this expansion from going past it. This causes the pressure in the water heater to rise very rapidly and quite high. One this pressure reaches the limit of the TP valve, it trips to protect the tank. In other words, it does its job. An expansion tank gives the expanding water a temporary home. Some newer water meters also have a check valve built into them to prevent the possibility of contamination getting into the city system. Try this test with the gauge. Connect it to a hot water faucet and turn the faucet on. Then open another hot water faucet to drain out some water from the heater so that it will begin heating. Watch the gauge as the water heats. It will probably scare the hell out of you!

    [​IMG]
    Last edited by a moderator: Jan 16, 2008
  6. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    the prv is functioning.. I can pull the handle up..and water will come out of the copper tube....
  7. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    I believe you are having a problem with translation of terms and abbreviations. A PRV is a pressure Reducing/regulating Valve on the main line just inside the house or at the water meter. The thing on the hot water tank is a pop off valve or pressure relief valve. If you have the back flow preventer or pressure ruducing valve at the meter or just inside the house, that is when you need the expansion tank. If the PRV pressure reducing valve on the main line is bad then the pressure in the entire house is too high, that is why they have you checking the pressure on a hose bib some place. You are checking the main pressure. If you don't have a pressure reducing valve or back flow preventer on the main line and nothing has been changed on the system lately, then the pressure relief valve or pop off on the hot water tank might be bad. You should be someplace just nort or south of 50lbs of pressure on the main line. The box store have cheap water pressure gauges the hook on to a hose bib just like a hose.
    Last edited: Dec 17, 2007
  8. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    nothing has changed lately...

    yes, I am talking about a pressure relief valve.

    I think when i was in the suburbs we were required to get a pressure reducing valve is we had a lawn sprinkler system installed

    I don't think this house has a pressure reducing valve... unless it is at the water meter... i can see the pipes coming in from outside... i do have an inline water filter..but that's about it..

    I'll do the relief valve after the holidays..
  9. SteveW

    SteveW DIY Senior Member

    Messages:
    1,052
    Location:
    Omaha, NE
    I too had this problem and in fact it was excessive pressure due to having a PRV on the main line as Gary and others above have said. Adding an expansion tank has kept house pressure at 60 psi - without the expansion tank, it would get well over 120 psi at times (i.e. when water heater was heating a big slug of cold water).
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,349
    Location:
    Yakima WA
    I agree there may be a misunderstanding of terms. The valve that is leaking, goes by several names, I think the most common is TP valve, short of temperature/Pressure relief. These are pre-set to 150 degrees and 75 psi and act as a safety devices to prevent the tank for blowing up. They can go bad and leak. The PRV that was referred to is a Pressure Regulator Valve that goes in the incoming water supply line to avoid having too much pressure which will damage fixtures. I'm not sure of all of the locations they may be attached, but I think the most common is right after the supply line enters the house. If you do not have one and your household pressure is less than 60 or 65 psi, you don't need one. Much above that pressure ranges you might want to consider one. TP valves are available at any hardware or plumbing store for about $15 and are easily change by a homeowner.
  11. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    Expansion tanks and PRV's fix two different problems. If you have high main line pressure an expansion tank won't fix that. If you have a PRV or back flow preventer on the main line then pressure will build up when the hot water tank heats the water and you will need an expansion tank, two cures for two different problems.

    In this case he does not have a PRV and does not have a back flow preventer and nothing has changed. He probably needs a new pressure relief valve.

    I would buy a cheap water pressure gauge just to check the main line pressure just to be sure the city didn't change some thing with out you knowing. If the pressure holds at around 40 to 60 lbs then it is probably just the relief valve. It is a quick easy check.
  12. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    thanks.. i will heed all of the advice.

    the folks on this board have gotten me through some major and minor issues..

    ...all with flying colors....
  13. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    Take a pressure reading using a lazy hand gauge that records the highest reading. Leave it on overnight. Frequently that is when the highest pressures are recorded. If it goes over 80 PSI you need apressure reducing valve>
  14. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    Releif Valve Leaking




    GARY YOU HAVE SOME OF YOUR FACTS WRONG ! !

    a T & P valve opens at a 150 psi. or 210% degrees which is 2 degrees below boiling temp. at sea level.

    the T & P weeping is caused by thermal expansion,

    if you have 1/2" to 1" household PRV. they all allow backflow onto city main!!

    but due to clean water act all city water "MUST" have one way check valve.

    so even if you had household pressure at 60 psi. and no PRV. you would still get thermal expansion weeping at valve

    also the MAX high water pressure by code is 80 psi.


    JERRYMAC MASTERPLUMBER P. H. D. IN WATER HEATERS


    MERRY CHRISTMAS TO ALL OUT THERE
  15. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    If it is an older house it has no backflow preventer. He said it has no back flow preventer. The tank never had a problem before, he said nothing has changed it is just the pressure relief valve going bad. Checking the main line pressure with a cheap gauge to make sure nothing has changed with the city is the only thing necessary, just in case. You don't want problems with faucets and valves if the pressure has increased. Beyond that a pop off valve is cheap so what's the big deal change it and see if it works.
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