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Thread: Water level drops in skimmer on low speeds

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    Water level drops in skimmer on low speeds

    I recently replaced my Whisperflo pump with a Pentair Intelliflo Variable Speed Pump. I'm not sure if this is normal or not, but there are two issues that I am noticing. First, when the new pump primes, it works great. The problem is when I drop the speed down below 2,500 RPM, the water level in the skimmer very slowly drops after an hour or two. If I decrease the speed to around 1,000 to 1,500, the water will eventually drop to the bottom of the intake port and will stay there.

    If the skimmer fills up with water and I turn the unit off, the next day the water level will also drop a few inches. I never had an issue with the Whiperflo pump. The water would always stay at the top.

    Another issue I am having is that when I run the unit at a slow speed, it knocks really bad. I can feel the pipe that goes to the filter and it has some heavy vibrations in it.

    Is this all normal?


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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Water level drops in skimmer on low speeds

    Welcome to the forum.

    Discounting a leak in your pool (which you don't seem to have), the only reason for the water level to change is if you have a suction side air leak and are capturing air in the filter.

    That really doesn't seem very plausible to me, though.

    While your description doesn't exactly fit, the other reason could be a restriction or blockage on the suction side that would show itself pump running but then would return to normal level when you shut off the pump.

    1. Do you have an autofill?

    2. Do you have a check valve in front of the intake side of the pump?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Water level drops in skimmer on low speeds

    When you say skimmer, are you talking about the strainer pot in front of the pump or the surface skimmer in the pool?

    I suspect it's the strainer pot.

    If so have you lubed the lid o-ring well and made sure it's seated tightly?
    Have you removed and resealed the pump basket drain plugs?
    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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