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water heater ?

jim lockard
jim lockard Member Posts: 1,059
on a well. In my area of the country the check valve is between the well pump and the pressure tank. Between the pressure tank and the water heater their is no check so the pressure tank is used for thermal expansion, placing a water heater expansion tank in the system would be of little value. The air cushion in the pressure tank will more the make up for any rise in tempturature. Your builder could rightly argue(IMHO) that he has installed an expansion tank on your system in the form of a pressure tank. Best Wishes J.Lockard


  • Andy_14
    Andy_14 Member Posts: 121

    My plumber put in our contract(new home construction) he would install an expansion tank on the hot water heater. His crew didn't use one. I asked them why, and they said since I am on a well and not city water, that it was not needed.
    Is this true, or do I need to have them put it in?
    Thanks, Tasha
  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    X tank on water heater

    Even a well system is a closed systemt that can allow pressure to build as the boiler heats the water heater. There is usually a check valve at the storage tank coming in from the well, so yes, and expansion tank is an excellent idea. It can prevent thermal expansion and a discharge from the safety valve. It should be a tank rated for potable water and installed on the COLD inlet side of the water heater. If he refuses to install one, get a credit if its in the contract and hire someone else to install it. Best if it's there when you need it.

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  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    location of check valve

    should be on the inlet side. Well water tanks, water heaters, etc. are very good at withstanding high pressures, but lousy when a vacuum is drawn! They'll collapse.

    As for a thermal expansion tank, if your well water expansion tank is sized properly (to provide a minimum of 1-minute's run time per pump cycle), an additional thermal expansion tank probably won't be required.

    The only way to know for sure, is to know the final air volume in the well water tank when at max pressure, which can be determined via Boyle's Law. Next comes the water heater's volume and delta-T between the 55-degree incoming temp and final storage temp, which will yield the multiplier needed to determine thermal expansion volume. Back to the well water tank & Boyle's law to determine final pressures once thermal expansion is adsorbed.

    You'll have, or should have, two relief valves in your system: a 75-Lb relief (only) at the tank-T; and a 150-Lb temp & pressure relief valve on the water heater.

    Your plumber is most likely correct.

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