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Two loops go to one in-floor zone, but one won't flow

I've got a 10 year old in-floor heat system. One zone has a manifold that sends water to two 1/2" PEX tubings and they both have flowmeters (same pump). This heat season one of the two loops will not flow - suspect air. I've drained water from the return side manifold (after closing the valve between the manifold and the boiler) multiple times, but to no affect. Experts and other Smart People, what should I be doing next to try and get that loop flowing. I'm in Minnesota and cold weather is coming, so thanks for the help!


  • hot_rod
    hot_rod Member Posts: 22,256
    Are there any zone Valves or actuators on the two loops? Also look for Valves to isolate the loops and purge the no flow one with pressure from the fill valve or a small transfer pump

    A pic or drawing would help see what you have.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • castover
    castover Member Posts: 17
    Thanks for the comment "Hot Rod". Sadly, there are no valves in the vicinity. It is just a manifold that sends two 1/2" PEX up to the 2nd floor and then two 1/2" PEX comedown to a similar manifold.

    There's lots of bubble removal equipment that works well at the expansion tank at the supply side of the pump, but I doubt there is anything between these two manifolds.
  • Paul S_3
    Paul S_3 Member Posts: 1,261
    When you say you drained water are you getting flow through the loop when you purge it ? Or no flow when the pump is on after you purged the loop?? Can you post some pics of the piping and manifold
    ASM Mechanical Company
    Located in Staten Island NY
    Servicing all 5 boroughs of NYC.
  • Zman
    Zman Member Posts: 7,573
    There is almost always a way to power purge the system. They had to get the air out the first time.

    Post a picture of the piping and hopefully someone can walk you through it.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Paul48
    Paul48 Member Posts: 4,469
    The secret to getting air out of a zone/radiator, is to create flow from one direction. You may have to add valves, and the system should have a means of automatic air removal.
  • castover
    castover Member Posts: 17
    I got it working! Duh... It turns out there were tiny valves on the return manifold and I throttled the loop that was functioning and then we were off and running. Thanks for the help guys, and until next time!