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Thread: expansion tank missing

  1. #1
    DIY Junior Member 68malibu383's Avatar
    Join Date
    Dec 2009

    Default expansion tank missing

    I looked at a 1997 house today and the original gas water heater had been replaced with a Rinnai tankless. House was on a slab and around here, the expansion tanks are at the water heater. I have a feeling the tank was removed and not replaced. From what I understand, a tank is not needed if one has a regulator with an internal bypass. This looked like a standard regulator but was wrapped in insulation for the most part. Do the bypass regulators have a return line? So there would be three lines connected to it total, right?

  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    You do NOT have to have an expansion tank with a tankless, because they do NOT have expansion problems. Internal bypass regulators only work if the city pressure is within the limits of a safe pressure. They do not have any additional lines, because it is "internal".


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