Grunfos Recirculating pump issue

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jzsjr, Apr 1, 2008.

  1. jzsjr

    jzsjr New Member

    Messages:
    9
    Hello,

    I have a grunfos recirculating pump that uses one's existing hot water cold water plumbing. It consist of the pump mounted above the water heater and a special valve mounted underneath a sink in our faraway bathroom. My issue is that when one flushes the toilet next to the sink that has the grunfos valve the pipe thumps when the toilet finishes filling. The one way to relieve the thumping is to open the cold water faucet on the sink with the grunfos valve. This then pulses the water for a few seconds. I installed some Chief arrestors on both water cut offs of the sink and an arrestor that fits on the water inlet of the toilet. I thought these helped out for a bit or lessened the degree of the thumping but overall the noise still exist. Is there something else I can try? I don't want to get rid of the system since it really does bring hot water instantly to the shower and that is a big deal in Atlanta now with our on going drought.
    thanks,
    Jim
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,804
    Location:
    New England
    The pipes themselves may not be anchored well. If you grab the shutoff, can you move it in and out of the wall? It should be fixed in place.
  3. jzsjr

    jzsjr New Member

    Messages:
    9
    I have exposed the the pipes to the sink and they were not fastened. I arranged a piece of wood and strapping and have them secure now. The pipe to the toilet just comes up through the floor and has some movement but not much. The horizontal pipe that approaches the toilet on the ceiling of the basement is secure. I'm not sure if my Toto toilet is pulsing and causing the issue or it is the grundfos recirculator because the noise continues but does not seem to be every flush. Is the next step to put an expansion tank in near the water heater? Do I remove the pump system and see if it continues?

    thanks,
    Jim
  4. jzsjr

    jzsjr New Member

    Messages:
    9
    When I turn the recirc pump off the thumping is still there but much slower and last longer. I don't see any pipes moving along with the thump. The noise also occurs when I simply turn off the faucet. This is with the local pipe arrestors in place.
    Jim
  5. srdenny

    srdenny Plumbing Contractor

    Messages:
    361
    Location:
    SF Peninsula
    Can you ascertain the exact location of the noise? Perhaps your strapping only helped part of the problem and there are more loose sections of pipe yet undetected.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,253
    Location:
    Cave Creek, Arizona
    thump

    Your problem is the toilet's fill valve and has nothing to do with the pump. You may need a slower operating fill valve such as the Fluidmaster PRO line, which only plumber's can purchase. "Professionals will find them innovative. Amateurs will not find them at all."
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