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Pressure in closed loop

I have a closed loop 6 zone heating system in 2 storey home. Circulating pump is on inlet side and air scoop and expansion tank are on supply side. Boiler reads 22psi. There is a pressure gauge at inlet of circ pump that reads between 12-14 psi depending on how many zones open(sucking). But when system shuts down this gauge slowly drops to zero, why? There are no visible signs of leaks anywhere. Any help would be appreciated.
Don B


  • STEVEusaPASTEVEusaPA Posts: 2,820Member
    I would think it could be air, or a bad pressure gauge, or a failing/undersized/waterlogged expansion tank.
  • ZmanZman Posts: 4,814Member
    Quite a few variables here, A drawing or picture would help.
    It would be normal for gauges on opposite sides of the circulator to read differently. After all that is what the circulator does.
    As Steve pointed out, a bad expansion tank would explain the pressure dropping as the system cools.

    For what it is worth,
    It sounds like you are pumping into rather than away from the expansion tank. This is not ideal.
    A 12 PSI difference across a residential circulator is quite a bit. What size circulator and what are you asking it to do?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • dbauerdbauer Posts: 3Member
    Thanks for your input, hope these pics will help
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