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Unwanted gravity circulation

Larry_35 Member Posts: 2
Hello -

I recently removed an ancient coal/gas conversion burner gravity hot water toiler and replaced it with a newer forced circulation gas boiler. I removed most of the humongous gravity piping and repalced it with 3/4 in copper and installed a Taco flow control valve in each of the four loops. Now I get a lot of gravity circulation when the circulators are off. The screws on the flow control valves are properly screwed down. The probelm is mainly with the second floor. Could the gravity "pressure" be overpowering the flow control valves? I paid a fair amount of money buying them to prevent this exact problem. Anyone have any idea what to do about this?


- Larry


  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Not all Flow Checks

    follow the "lefty-loosey/righty-tighty" dictum. Some have RH turns to open them by depressing the closure spring. Going to the left releases the spring so that it can bear on the clapper. The "fully open" feature is geared to allow gravity flow in power outages.

    You may well have fully opened the flow checks.

    Have you tried going the other way? No, not like that.

    I mean turning the knurled knob all the way in the opposite direction.

    Remember Newton's Fourth Law: "Gravity Wins".
  • John@Reliable_14
    John@Reliable_14 Member Posts: 171

    I would "open" flo-check and purge zone(s), doesn't hurt to hit valve alittle while purging to dislodge anything stuck on seat, doesn't take much to hold open flo-checks.Sometimes when all else fails a second check on other side of first one will stop flow. (if now on return/add one to supply too) but I bet you have something stuck in it.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Don't forget that a simple "heat trap" will stop--or at least greatly diminish--gravity flow. The only expense is some added piping and added delta-p. See image.

    12" of trap depth in a re-piped gravity system using modern pipe sizes should be more than sufficient to stop gravity flow even to a 3rd floor radiator.
  • rob brown
    rob brown Member Posts: 69

    larry, are you sure they are piped properly? flo-checks work by virtue of a weighted flapper.if that thumbscrew isnt pointing straight up they wont work. rob
This discussion has been closed.