Water heater leaks out pressure relief valve

Discussion in 'Water Heater Forum, Tanks' started by Mcheil83, Apr 30, 2014.

  1. Mcheil83

    Mcheil83 New Member

    Messages:
    3
    Location:
    Pennsylvania
    Hi everyone hopefully you guys can help me get to the bottom of this. I had an old hot water heater that leaked from the pressure relief valve so I installed a new pressure relief valve & it still did it, installed a heating element same thing, installed a thermostat same thing. Nothing worked so we bought a brand new hot water heater and the heater doing the same thing the old heater did, it's leaking from the pressure relief valve. It would be greatly appreciated for any help. Thanks Matt
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,438
    Location:
    IL
    You have a check valve in your system. You need an expansion tank to accommodate the expansion of water.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    Check valves are usually found in pressure regulator valves and sometime in late model water meters. These prevent possible contaminated water from getting from the home and into the water mains. These valves create what is referred to as a closed system. What happens in a closed system is the expansion caused by the heating water is prevented from being absorbed by the city main. This expansion has to go somewhere, so the T/P on the water heater opens to release the excess pressure. The amount of water is fairly small, but can damage floors. The thermal expansion tank goes in the incoming water line prior to reaching the water heater and stores it until the pressure is normal again. These tanks are not very expensive, last time I checked they were around $50-$60. Simple DIY to install if you can sweat a copper joint. Don't expect a plumber to be cheap on the labor, but if he is already there, you might get by without an extra service call charge. Installation instructions are on the box.
  4. Mcheil83

    Mcheil83 New Member

    Messages:
    3
    Location:
    Pennsylvania
    Ok thank you guys soooo Much I will try that ASAP



    :eek:
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    I went through this several years ago and did just what you did. Replaced the T/P and still had the problem. That's when I learned about expansion tanks. I had just put in a pressure regulator valve and the trouble began. Went to Lowe's and discovered they had never heard of expansion tanks!!! Went to HD and had my pick of sizes. To my knowledge, Lowe's still does not stock them. (That's in my city anyway) You need a pressure gauge to adjust your PRV and charge the expansion tank to match the PRV setting. I have mine set at 50 psi, some like a tad more pressure, but that seems to be plenty for me.
  6. Mcheil83

    Mcheil83 New Member

    Messages:
    3
    Location:
    Pennsylvania
    Hey Gary does the expansion tank come with the pressure gauge or is that something extra I'll have to buy. This is my first house so a lot of this is all new to me. Sorry for all the questions.






  7. Reach4

    Reach4 Well-Known Member

    Messages:
    2,438
    Location:
    IL
    You probably want a pressure gauge like this: [​IMG]

    Then you will also use a tire pressure gauge and maybe a tire pump to set the pre-charge on the expansion tank to the same pressure as the PRV is set for. Adjusting the pre-charge on the expansion tank is done with the water turned off and zero pressure in the pipes during that process.
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    Pressure gauges are available at most any hardware or plumbing shop. Not expensive. I actually installed one in my water line so I can see at a glance how the pressure is holding. Not necessary at all, you can just connect it to any faucet with hose threads. In fact, connect it to a hot water faucet and run some hot water from another outlet. When the water heater kicks on, watch the gauge. You will be amazed at how fast and how high the pressure rises. The pressure in the expansion tank is checked just like a tire with a tire gauge.

    Added after the above.
  9. Wallijonn

    Wallijonn Member

    Messages:
    147
    Location:
    Arizona
    What I learned from water pressure this weekend when I removed my old water heater:

    I turned off the WH ball valve.

    When I started to drain it, opening all the faucets in the house had little effect on the water quantity coming out of the hose. When I turned the TPRV to the middle position it allowed quick draining (1 hour instead of 4).

    Since it was draining, and since the WH valve was off, I needed to wash my soiled hands. I turned on the house main to wash my hands.

    I had a drip in one of the bath faucets in one of the bathrooms, which I heard as I was watching TV while the WH drained. As I'm watching the drip the toilet inlet water hose splashed some water on the floor. What the heck???

    I go over to the WH and notice that water is going back into the tank through the hot water line. What the heck?

    It seems that the mixing valves on my bathtub/showers are allowing cold water to pass through to the hot water line. Because the faucet isn't turned on the hole between the cold and hot water mixing valve is small - so the water pressure went up.

    I turned off the house main, removed the old ball valve on the WH cold water inlet, and installed ball cocks on both the cold and hot WH inlet pipes at the wall.

    When I turned on house main I no longer had the high water pressure.

    So, what am I getting at? You have high water pressure. It may be that you need to replace all the mixing valves in your house (kitchen sink where you have a single handle to control the cold/hot water coming out of it, or the mixing valves in your bathrooms, either at the vanities or the bathtub/shower, if you have them at all. You may even have one, although very unlikely, at the clothes washer. It may be that even though the handle is turned off that the mixing valve is allowing cold water to pass through back into the hot water line. That would create high back pressure at the WH, and once there is any type of small leak at the WH the pressure will actually increase.

    Once, a radio announcer asked why when first turning on a shower the water in AZ feels hot. It's because of the mixing valves. It was 100ºF yesterday in Phoenix. When I went to take a shower at 9PM all I had available was cold water (because I haven't finished installing the WH), and let me tell you - the water was cold. I know that once I turn on the WH the water will go back to "hot" the second I turn on my shower. And that's why it's better if you don't have mixing valves in the home, in the kitchen or in the bathrooms. If you have any leaks on any of the mixing valves anywhere in the house - that's where to start replacing them.
    Last edited: May 5, 2014
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