continuous "relief" from t&p valve

Discussion in 'Water Heater Forum, Tanks' started by srichey01, Feb 5, 2009.

  1. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    I have a 50 NG American W/H in house when we bought it and approx 5 yrs old. After 4+ yrs of no problems, my T/P valve started continously "relieving" itself on my basement garage floor. I have replaced the Thermostat unit (warranty), flushed the unit and adjusted the temp setting and incoming water flow, all trying to prevent stacking. Would replacing the T/P valve be a prudent step or should I just get a new heater.
  2. Redwood

    Redwood Master Plumber

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    7,453
    Location:
    Connecticut
    I only fix things that are broken.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    14,775
    Location:
    Bothell, Washington
    If the T&P is letting water out,

    you may have a bad or worn T&P
    Or perhaps there is an expansion problem.

    If the system is "closed", then an expansion tank is needed.

    A system can be closed by a check valve (some new water meters have checks built in), a back flow preventer, or by a pressure reducing valve.
  4. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    I can only assume the system is closed. I am going to try replacing the t&p valve and also will install an expansion tank. Hopefully this will solve my problem of continuous water from my relief valve. Thank You for you help.
  5. Cass

    Cass Plumber

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    5,980
    Location:
    Ohio
    Do you know how to correctly install an expansion tank...
  6. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221

    Yes you should buy a new T&P valve and change it, but skip the expansion tank for the moment. Buy a water pressure test gauge so you can measure water pressure. The cost is under $30 for both.

    I had to change my T&P valve last Thansgiving!
  7. dough41

    dough41 New Member

    Messages:
    3
    My water heater also recently started leaking thru the T&P valve. I changed it out and still the leak. Not thinking that the extra heating zone I added in the in the basement over the summer would cause an expansion problem (I had only one expansion tank for my closed system hot water boiler) I was scratching my head. I posted the problem here, then the light went on when someone mentioned an extra expansion tank.I added a small therm x trol in the cold water supply before the heater and well its been a few days ( knock on wood) and problem seems solved- no more dripping TPR valve. Hope this helps.
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
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    Location:
    Yakima WA
    You only need an expansion tank if you have a closed system. If there is no PRV or other check valve in the system, the expansion will be absorbed by the city water main. T/P valves do go bad, so that may be your only problem. I would tend to suspect a bad valve unless something has been done to the water system recently to create a closed system. Fortunately, T/P valves are inexpensive and are easy to change.
  9. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    new valve

    I just finished replacing the t&p valve. time to wait and see. as far as the expansion tank, i did not buy one yet. however the way the w/h was installed i do not know if i will have enough room. it is installed in the corner of my basement garage (direct vent), i have approx 17" clearance to the ceililng and approx 7" clearance from the cold line to the wall....will that be enough room to install the expansion tank? Hopefully the new t&p valve will solve my problem and I will not have to find out. I Thank everyone again for your assistance.

    [​IMG]
    T&P Valve looking at two sides.
    Last edited by a moderator: Apr 24, 2009
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
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    Location:
    Yakima WA
    Have you determined whether or not you have a closed system. You seem to be evading that question. If you do not have a closed system, then there is no point in installing an expansion tank, and no point in attempting to address the how-to-install question.
  11. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    I apologize gary, i was not trying to avoid the question, i guess my haste to get the T&P valve changed to stop the steady flow took over my thought process. i do not see any sort of check valves from the main water line coming into the house. there is also nothing on the cold line to the water heater. i believe it is not a closed system
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    Some munidipalities install the water meter with a check valve, either integrated, or add-on, so you may not be aware of it. T&P valves do fail or weaken, so they can dump water. Keep in mind that they are designed to release water under two different conditions: excessive pressure OR temperature. Checking the pressure isn't too hard - gages are cheap. Temp may be harder, but thermometers aren't expensive, either. If it was just getting old and weak, or the seal is bad or the shaft is corroded, it might not allow it to seal, and it could weep or leak. If a new one doesn't fix it, install an expansion tank after checking pressures and verifying the thermostat is working properly.
  13. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    Go to your local hardware store and buy a pressure gauge and adapters to a female hose connector. Screw this assembly to a hot water faucet and turn the faucet on and note the pressure. This will be your normal pressure. Now drain enough hot water from another faucet to cause the water heater to start to heat. Watch the pressure gauge. If the temperature rises to 150 PSI, the T/P should open. This would indicate a closed system. If the T/P trips at a lower pressure, replace it.
  14. Terry

    Terry Administrator Staff Member

    Messages:
    14,775
    Location:
    Bothell, Washington
    If the system worked before without the expansion tank, it may not be needed.

    If you had replaced the T&P and it hadn't worked, then it would be the next step.

    Sometimes T&P's just get old, or the seat on them gets crud on it and won't seal. They're pretty easy to replace though.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,264
    Location:
    Cave Creek, Arizona
    leak

    Unless you tested the system to find the actual cause of the symptom, most people WOULD replace the T&P valve FIRST.
  16. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    i believe all is good (knock on wood). No leaks from the T&P since replacing it yesteray around noon. I want to thank everyone for your help. You saved me bunch of money because I would have just went out and bought a new w/h which would have been 700-800. Thanks again. Next task is replacing the timer on the dishwasher. Everything happens at once.....

    Scott

    [​IMG]
    T&P Valve looking at two sides.
    Last edited by a moderator: Apr 24, 2009
  17. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Even though it seems like you do not have a closed system you need to check your water pressure...unless you do you may be shortening the expected life of the heater...buy a pressure gage and check the pressure...I doubt you know what the incoming water pressure is...
  18. srichey01

    srichey01 New Member

    Messages:
    6
    Location:
    Sevierville, TN
    i planned on doing that today...getting ready to head out and pick up a pressure gage and test it out.
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,264
    Location:
    Cave Creek, Arizona
    heater

    quote; You saved me bunch of money because I would have just went out and bought a new w/h which would have been 700-800.

    Which is EXACTLY why I tell people to find out WHAT the problem is before doing anything. You had already changed a perfectly good thermostat, which the company paid for, without curing the problem.
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