What is the best position for a potable water expansion tank?

The Tank What is the best position for a potable water expansion tank?

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  • #14492
    AkBrian
    Participant

    A number of years ago the local water company changed from an open system to a closed system when they changed out water meters, as in they added a foot valve after the meter (the meter is in the basement, due to the cold climate). I never thought anything about it till I happen to notice my 25 year old 30 gallon electric hot water heater dripping out of the TP valve into a floor sump. A little googling suggested checking my water pressure. 25psi static, and a scary high of 125psi under the right (wrong?) conditions. So I bought a Watts PLT-12 potable water expansion tank. I’m trying to figure out how to best mount it. Will it last longer mounted inlet down or up? I just want to do this once..

    #14493
    Randy Schuyler
    Keymaster

    You can put it anywhere as long as it’s not right on top of the water heater. Hot water drawn into it by convection will wear out the rubber diaphragm more rapidly. Also, it’s time you checked the anode in that water heater!

    Randy Schuyler

    #14495
    AkBrian
    Participant

    Thanks for the reply. I think it’s a good time to just go ahead and change the whole water heater, seeing how I’ve neglected it all these years. I’d hate to start changing all the parts, then have the tank fail, but I want the to fix the pressure problem before I install a new tank. I have a wall that I can mount the expansion tank on, and can set it up either inlet down or up, or sideways, just not sure which is better. Sounds like perhaps it just doesn’t really matter.

    #14502
    Larry Weingarten
    Participant

    Hello: There are differing opinions on this. My opinion is to mount the tank above the pipe it’s hooked up to. This way any debris does not collect in the tank. I’d also put a valve between the tank and pipe so air charging and any maintenance become easy.

    I’ve got heaters out there over fifty years old. Yours is old but not necessarily over the hill 😎 No doubt you have good water, even if it’s at only 25 psi.

    Yours, Larry

    #14517
    AkBrian
    Participant

    Thanks Larry, this has been helpful.
    -Brian

    #14524
    energyexpert
    Participant

    Brian,

    I’d also consider a pressure regulator. Public pressure can vary widely as you have testified. A regulator will prevent the surge from the supplier and then the expansion tank can handle volume changes due to heating of water. Expansion tanks are designed to operated over a narrow pressure range (like 40 to 60 psi typical of a well pressure switch). Swings of 100 (25 to 125) is not healthy on anything in a plumbing system.

    David

    #14525
    AkBrian
    Participant

    Thanks EE, I’ve concluded that the utility’s PRV isn’t working the the way it should (as I understand it). Regardless of how low it is set, pressure on the cold side (with HW powered off and valve closed) the pressure in the cold water system rises dramatically with time. like from 20psi to 70psi in about a half hour.

    #14527
    Larry Weingarten
    Participant

    Hello: I’ll second EEs thinking on pressure regulators. You would get more even water pressure if you put a well tank downstream of the regulator rather than just an expansion tank. To me a well tank is simply a big expansion tank. It would serve as an accumulator and allow you to be less affected by weird pressures in the supply system 😎

    Yours, Larry

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