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Expansion tank location

JohnybcoldJohnybcold Member Posts: 8
I am installing a gas boiler with 2 zones the house never had one it had a space heater so I am installing evrything the boiler manual says to install the expansion tank 18" away from the boiler, the boiler is in a tight spot how important is the 18"? I cannot find any info online related to exact locations for the install does it need to be above the boiler?

I have a 47000 btu gas boiler 2 zones heating a 2nd flooor apartment boiler is in the basement about 45 feet of baseboard


  • wcs5050wcs5050 Member Posts: 126
    expansion tank should be on supply side, connected to water pressure redux/backfloow feed point, and preferably air eliminator. 18 inch distance is in reference to cast iron air scoop that needs that for air bubbles to rise to top of pipe and be caught by air scoop. if you use a spirovent, taco 4900, etc., the 18" is unnecessary. with such a small boiler, you could probably use a size 15 expansion tank.
  • hot_rodhot_rod Member Posts: 13,903
    Where is the pump located? On some boilers they are on the return, others on the supply.

    The expansion tank connection should be close to the inlet side of the pump, regardless of where it is located supply or return.

    The tank itself could be mounted remotely, just pipe to it with 1/2" copper or pex.

    The air elimination devise should be on the supply side of the boiler, the hottest point in the system.

    As esc mentioned a micro bubble type separator is ideal, no piping distance required in front or downstream of that type air eliminator. they do a much better and faster job of removing air, compared to a cast iron ramp type air purger.

    Plenty of good brands of separators out there, here is one with unique features.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • JohnybcoldJohnybcold Member Posts: 8
    Thx for all the help the pump is on the return side just one pump the feed side has a manifold with two zones (taco switch on each) then goes to pex
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