Water heater Pressure Relief Valve open up

Discussion in 'Water Heaters and Softeners' started by bdmeyer, Feb 17, 2019.

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  1. Apr 11, 2019 #41

    bdmeyer

    bdmeyer

    bdmeyer

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    I finally got around to replacing the T&P Valve. As I was shutting the cold water off I noticed something I hadn't before. I seem to have to cold water lines that run together at the heater. Once has the cut off valve, the other doesn't. Turning the valve off did stop pressure to the tank. I'll be darned if I have any idea at all what the second line is for. I also noticed the copper pipe with the cutoff valve has something that looks like a solenoid maybe with '50 psi' printed on a green and white metal disk at the top. It has been 2 weeks since I replaced the valve. I ran all water sources in the house until all the air was gone. I only get a little bit of water out of the new T&P valve now. This is discouraging, but it is a small amount. Maybe 1 inch in the bottom of a 5 gallon bucket in two weeks. I do have one weird thing. When I flush the upstairs toilet now the pipes (not the toilet) upstairs make a moaning like noise until the tank is full. Today, the other upstairs toilet started doing this. The first toilet started doing it the very first night. If anything, I expected a water hammer. I don't have that. Call me mystified. I have never heard this in any house I've lived in. Thank you for any idea's you may be able to offer folks.
     
  2. Apr 11, 2019 #42

    Diehard

    Diehard

    Diehard

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    Well I'm not surprised.
    I don't like to jump to conclusions but it has sounded all along like the problem was that the hot water had no place to expand to.
    You never took pictures as requested so we were never able to see what you have. Now it sounds like you may, in fact, have a PRV(pressure reducing valve) on the cold water line. If that's the case you should have an expansion tank.
    Take a picture of those 2 lines you say that run together at the heater.
     
  3. Apr 11, 2019 #43

    bdmeyer

    bdmeyer

    bdmeyer

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    Hey Diehard!
    I just went through every single post, and here is what I read:
    On Feb 17, Diehard asked if I have an expansion tank on the water heater.
    No picture requested.
    On Feb 18, I stated:
    I haven't seen any type of an additional tank, so I am guessing it doesn't have an expansion tank.

    I don't see anyone requesting a picture. However, it sounds like you would like one, so I took pictures just now of everything I can see before it disappears.
    Here are some pics. Feel free to ask for more, it will be my pleasure!
    Thanks for all the help Diehard.
    -= Bruce

    20190411_172824.jpg 20190411_172834.jpg 20190411_172841.jpg 20190411_172851.jpg 20190411_172933.jpg
     
  4. Apr 11, 2019 #44

    Diehard

    Diehard

    Diehard

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    Yes that item with the green tag is a pressure reducing valve(PRV), factory set at 50 psi. That prevents water from expanding back into the city water supply. Without that PRV the water would typically expand back into the city water service when expansion takes place due to heating of water.
    (I should mention that although some PRV's come equipped with a "bypass feature that controls thermal expansion pressure", they would not necessarily be capable of keeping up with the rate of expansion.) just thought I'd mention that in case you saw some reference to this somewhere. In fact, just looked up your model number and it includes this note. "NOTE: The bypass feature will not prevent the pressure relief valve from opening
    on the hot water supply system with pressure above 150psi (10.3 bar)."

    So now we must have an expansion tank to allow that expanded water to go somewhere when heated. That tank, if it exists, could be located anywhere down stream of that PRV.
    If you do, by chance, locate a small tank on your system somewhere, chances are it became water logged. Meaning it got full of water and lost it's air, which allows for the expansion.

    By the way, that other line that comes off after that shut off valve likely feeds other parts of the house. Not going to the water heater.

    So you ended up with a spare P&T Relief valve.

    Let use know if you see something that could be an expansion tank. May look something like this.
     

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    Last edited: Apr 11, 2019
  5. Apr 11, 2019 #45

    Diehard

    Diehard

    Diehard

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    Oh BTW...check out post #30 and #34, regarding pictures.
     
  6. Apr 12, 2019 #46

    bdmeyer

    bdmeyer

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    I stand quite corrected. I never saw any of those posts. I was out of the country for 2 weeks, then traveling another two, without access to email accept by a phone. I just read them all. Legionella? (Legionaires disease?)
    I noticed this morning when I click on the link in the email, it only showed a small few of the posts, which is was I also did last night. I had to login to see all three pages.
    I am clueless where they could possibly have hidden that expansion tank. The copper lines go straight to the ceiling, then across and from there are hidden between floor and ceiling. If I understand what I've read here, since I have the Pressure Reducing Valve that means I almost certainly must have an expansion tank? I'll search again and post my results. Thanks for bearing with me.
     
  7. Apr 12, 2019 #47

    Diehard

    Diehard

    Diehard

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    No problem!
    As you found out the hard way, I believe it's fairly clear the reason that relief valve was spitting water was due to the lack expansion capabilities. With or without an expansion tank.
     
  8. Apr 13, 2019 #48

    bdmeyer

    bdmeyer

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    I did a thorough and careful inspection of the cold water line last night. I followed it from where it enters the house, across the ceiling to the water tank, back out of the mechanical room across the ceiling and then where it disappears between the ceiling and floor above. I checked under each sink through the entire house. I never saw an expansion tank. The 'moaning' noise seems to have disappeared now. Possibly brought on by air introduced when I shut the water off to replace the T&P valve? What would your recommendation be at this point, call a plumber and get an expansion tank installed? Invest in a small 5 pound sledge hammer? :)
     
  9. Apr 14, 2019 #49

    Diehard

    Diehard

    Diehard

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    An expansion tank is typically located close to the water heater, although it doesn't have to be.
    Although it's a fairly straight forward add-on, it would probably be best if you had a plumber do it for you.
    The plumber should know what size tank and pre-charge pressure is required for your specific case. But for your info and/or to double check the plumber, you can estimate the minimum size required yourself. You need to know the size of the water heater tank, the water service pressure and the maximum temp you set it to.
    Then look it up in the attached chart or any other manufacturers sizing chart.
    The tank should come pre-charged with air to 40 psi as standard. And would typically require that air pressure be raised to match the water service pressure. In your case I believe 40 psi is what you have.
    It's good to have an understanding of what's going on and why, even when someone else is doing the work for you.
    Exp Tank Sizing.jpg
     
  10. Apr 14, 2019 #50

    bdmeyer

    bdmeyer

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    Thank-You (all!) very much for sharing the benefit of your experience and knowledge.
    I think it's time to pass this on to a local Professional now.
     
    MASTRPLUMB likes this.

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