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    vbender's Avatar
    vbender Posts: 1, Reputation: 1
    New Member

    Nov 17, 2018, 10:40 AM
    Hot water tank has too much pressure
    I have a hot water tank (gas) that seems to be building up too much pressure . I replaced the pressure relief valve thinking that the valve was failing , but the tank still builds up pressure and lifts the pressure relief valve . What else would be causing this issue?
    ma0641's Avatar
    ma0641 Posts: 15,680, Reputation: 1012
    Uber Member

    Nov 17, 2018, 12:06 PM
    Could be a bad PRV valve. Check water pressure at the hot water drain.
    massplumber2008's Avatar
    massplumber2008 Posts: 12,776, Reputation: 1210
    Senior Plumbing Expert

    Nov 17, 2018, 12:23 PM
    Hi Vbender

    My guess is that you have a potable water EXPANSION TANK that has blown its diaphragm. Here, in some "closed loop" water piping systems we will install an expansion tank into the cold water inlet to the water heater (I've also seen a couple installed on the hot water piping) to absorb the expansion of the water when it gets heated up and has no where to expand, too. In most cases, the way we know that the expansion tank is blown is because the T&P valve periodically spits out a little water when the water heater turns on (or hot water gets used). Check for an expansion tank... if you have one, most likely it needs to be replaced.

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    Replacing an expansion tank is an easy job. Just shut off the water main, drain water from the pipes in the house, drill a hole in the top of the expansion tank and then a hole in the bottom of the expansion tank and drain the expansion tank of water. Once the expansion tank is drained it will easily unscrew for disposal.

    Post back if this helped!

    Milo Dolezal's Avatar
    Milo Dolezal Posts: 7,187, Reputation: 522
    Plumbing Expert

    Nov 17, 2018, 05:34 PM
    In addition to the above advise: Also your thermostatic valve on the water heater itself, could be failing


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