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Older expansion tank

Snowmelt Member Posts: 1,334
Went to a house with an older expansion tank that is mounts between the joist, also noticed there was no gauges or pressure relief valve . I went for a no heat call, pump was shot. No air separation either.
I don’t want to scare the customer financially but I’m going to have to tell him he needs a pressure relief valve and a gauge but to change the tank to a typical 4.4 gallon expansion tank just cut old one out and install the 4.4 gallon or am I missing something?


  • STEVEusaPA
    STEVEusaPA Member Posts: 5,688
    edited October 2019
    Little confused.
    Why do you need a new tank?
    What does 'no air separation either' mean? Do you mean no air eliminators? You wouldn’t necessarily have one with a steel expansion tank and column radiators.
    As far as a new tank, ideally you’ll want to be pumping away from the expansion tank. However on older boilers usually the circulator is on the return, and the old steel expansion tank is piped off of a tapping on the boiler, which is the opposite of what you want.
  • Snowmelt
    Snowmelt Member Posts: 1,334
    That’s exactly how it is, so I will just leave it. Yes no air elimination, the house was small and has baseboard with bleeders, so I am going to add a pressure temp gauge
  • Steamhead
    Steamhead Member Posts: 15,330
    If the tank is piped off the top of the boiler, that's your air elimination. Not as sophisticated as an air separator, but often it's enough. Some boilers have a cast-in baffle to make this setup work better.

    I personally prefer plain steel tanks. Unlike diaphragm or bladder tanks, they almost never need replacing. If you install an Airtrol tank fitting where the expansion line from the air separator connects to the tank, and a proper tank drainer in the other tapping, it will almost never waterlog, and if it does it'll be much easier to fix than replacing a diaphragm/bladder tank.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
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