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Thread: Reverse Water Hammer

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    Join Date
    May 2008
    Location
    Tallahassee, FL
    Posts
    2

    Reverse Water Hammer

    After 30+ years of use, my system has developed a peculiar habit when the pump shuts down. The back flow into the skimmer is so violent that it knocks my skimmer basket out of position, or when I am running my Navigator it will push the hose out of the suction line. Anybody else have this problem or even heard of it?
    Petey

    21K Vinyl In-Ground, 37 years, Hayward 3/4 HP Super Pump, Sta-Rite 75 SF Cartridge Filter, GE Digital Timer, BB&B.

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
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    37,879

    Re: Reverse Water Hammer

    Welcome to TFP!

    That is almost always caused by air accumulating in the filter. Open the air bleed valve on the top of the filter and let air out until a steady stream of water comes out. If the filter fills up with air over and over you must have an air leak somewhere on the suction side of the pump.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Mod Squad Bama Rambler's Avatar
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    Jun 2009
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    SouthWest Alabama
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    22,347

    Re: Reverse Water Hammer

    Pretty common actually. You have an air leak, and the air is getting in your filter. When you shut the pump off the air blows back out of your filter causing the skimmer basket to launch out of the skimmer.

    Common places to have an air leak:
    The pump strainer basket lid. Clean, inspect and lube the sealing surface & o-ring.
    The pump basket drain plug(s).
    The skimmer weir not working properly. Sticking is a culpret.
    The water level allowing the skimmer to create a vortex sucking in air.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    ivyleager's Avatar
    Join Date
    Sep 2007
    Location
    Raleigh-Durham,NC
    Posts
    489

    Re: Reverse Water Hammer

    I get some blow back when I turn off the pump, but the pressure (and a splash of water) goes out via pump basket lid. Instructions state to not over tighten and I never do.
    CaryB
    36 x 18 IG vinyl, 25K, 1 HP pump, sand filter
    1 skimmer, 2 returns, no main drain
    Old school: PoolSolutions test kit

  5. Back To Top    #5

    Join Date
    May 2008
    Location
    Tallahassee, FL
    Posts
    2

    Re: Reverse Water Hammer

    Thank you...I will begin the search tomorrow.
    Petey

    21K Vinyl In-Ground, 37 years, Hayward 3/4 HP Super Pump, Sta-Rite 75 SF Cartridge Filter, GE Digital Timer, BB&B.

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