Loud clunk when humidifier turns off

Discussion in 'HVAC Heating & Cooling' started by rschmitty, Feb 16, 2009.

  1. rschmitty

    rschmitty New Member

    Jan 24, 2009
    Recently I had a humidifier repaired, it needed a new solenoid. The humidifier never worked since we moved in but now that it is working, anytime it shuts off there is a loud clunk that can be heard around the house.

    When I stand in front of the humidifier it doesnt sound as loud as I would have expected, seems like its coming from inside the pipes? Not sure how to describe it

    Is this normal or is there something I can do or adjust?
    Last edited: Feb 16, 2009
  2. Hube

    Hube New Member

    Sep 1, 2004
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  4. rschmitty

    rschmitty New Member

    Jan 24, 2009
    oops.. 'now that its working'

  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    You may need to add a water hammer arrestor in-line. Solonoid valves open and close quickly. Opening isn't usually an issue, but closing can be - water has inertia...and it wants to keep moving. It will have to stop quickly when the valve closes, and this can cause things to move.

    A hammer arrestor has a piston and a sealed air chamber or an air bladder (depends on the type). It needs to be installed close to the offending valve. But, it will be a long-term solution that should fix the problem. Sioux City, Watts, and others make them. They aren't particularly expensive ($10 or so), and should solve your problem, but they do require installation.

    Last edited by a moderator: Feb 22, 2009
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