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check valve problem

WAYNE M Member Posts: 7
have a problem on a condenser water line,8" size, customer had us remove 8"triple duty and replace with nibco 8" check valve & 8"nibco balance valve

the check valves "chatter" and do not hold.

we have replaced checks but problem persists

looking for ideas why it chatters and how to solve

also what is a flow straightener


  • Jamie Hall
    Jamie Hall Member Posts: 23,446

    I'm presuming this is a swing check, like the F-938 series?  If so, the most likely cause of chatter is insufficient pressure differential across the valve.  It's been decades (really) since I was much involved with bigger checks, but that is the concern I always had in those days about plain vanilla swing checks.  For which reason I always used either checks with an outside arm for a weight or a spring or -- preferably -- pilot operated checks such as the Cla-Val 100-04

    It might help if the valve was oriented so that gravity assisted closing (flow up).  If you can do it...  Otherwise... dunno.

    A flow straightener is any one of a variety of piping specialties which are designed to eliminate the turbulence downstream from an elbow, T, globe type valve, etc. etc. etc.  They come in quite a variety of flavours; only time I used to use them was upstream of a venturi or orifice meter when I couldn't get the straight length (at least 5 diameters) I needed.

    Don't know if any of that helps any...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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