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Taco internal flow check catching air. Does anyone else have this problem?

Adk1guy Member Posts: 66
My service dept jumped on the internal flow check bandwagon.
There is a repeated problem we run into, when we have the pumps pushing supply water away from the expansion tank, the first pump in the path of an air bubble occasionally becomes air bound. The internal flow check is so close to the impeller there is no place for the air to go and the impeller, being air bound, can't push water and move the tiny bubble into the system where it would be harmlessly absorbed and be removed by the air eliminator the next trip around.
A service call amount to blowing a few ounces of water out a purge valve. This happens several times a year. The old school method of installing a flow check valve downstream of the pump allows the small burp of air to rise out of the pump and be pushed through the old school flow check.
Does anyone else experience this? Do you have a fix?


  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    Yes, I have had that happen as well...more than once. 

    I now no longer use inter flow checks. 

    I've also had them rattle which makes me look bad to a customer. This is both on Taco and Grundfos. 007, Alpha1, 0015, all the common pump sizes. 

    I went back to using weighted flo-checks. Iron, and the bronze sweat-check. Problem solved. 

    Always put a weighted check after the circulator, I like to put them a foot or more away on the supply. You can put them all on the returns, with the circs on the supply, but you can get heat migration. 

    Generally, I use zone valves so flo-checks aren't needed. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • GroundUp
    GroundUp Member Posts: 1,941
    Why is there air in the system? If you'd completed a proper install and startup, this would never be an issue. IFC are awesome, I use them on every system with multiple circs. No rattling, no air issues, and best of all, no ghost flow or backflow.
  • hot_rod
    hot_rod Member Posts: 22,382
    I agree, a check should be 12 pipe diameters downstream of a turbulent condition, like a centrifugal pump discharge. The vertical, pumping up, orientation seems to be most prone to air locks. Sometimes it is a first start in the fall that is a problem as any air migrates to the check and volute.

    A days worth of high temperature operation with a properly piped and pressurized system and a good microbubble purger is the best protection. Some air entraining hydronic conditioner may help also.

    Checks in the iso flanges are not much better.
    A swing or weighted check will also cause problems if mis-applied. The Cv of a check is in the full open position. 5 gpm thru a 10 Cv swing check will cause the flapper to be partially opened.

    Low or variable speed pumping may also have a problem, "popping" or holding a spring check fully open, hence the chatter.

    Some best practice suggestions.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Joe Mattiello
    Joe Mattiello Member Posts: 707
    Usually air collects when pumping downward, is that the case?
    if the problem continues, I’ve seen contractors drill a small pinhole in the check to allow air to continue towards top of system. 
    Integral checks are awesome 99.9999% of the time. Feel free to reach out to Taco tech support at 401-942-8000 for more help. 

    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • hot_rod
    hot_rod Member Posts: 22,382
    This has been my experience. The pump becomes a high point air trap. Maybe we need the Runke pump/purger assembly.

    Just be careful drilling checks, I've had checks and zone valves cause overheating with even a speck of teflon tape lodged in them keeping them open a crack.
    Use a very small drill :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • pedmec
    pedmec Member Posts: 994
    i never had a problem but i generally oversize my manifold so velocity is reduced and air is allowed to separate and rise, allowing air vent out of any separators. i would look at your piping size on the suction side of circulator. you could be having velocity issues.
    STEAM DOCTOR Member Posts: 2,022
    Had some issues when they first came out. Can't remember last time that we had an issue. 
    EBEBRATT-Ed Member Posts: 15,764
    We have had rattling complaints on pumps shipped with the mod cons (the boiler circ) Mfg told us it was common to remove the check valves