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Thread: Good outflow, low suction...

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    Good outflow, low suction...

    I hope someone can help me with what I consider a weird problem. Inground pool, 1 1/2 hp pump, sand filter. I just returned to my vacation home and needed to vacuum the pool. (vacuum through the skimmer opening) In the past I have had good suction. Now I have very little suction. I have no separate inline valves controlling the bottom drain and skimmer...both connect to each other under ground and a single line runs to the pump input. So the only way I have to draw suction only from the skimmer is to cover the bottom drain. I tried covering it with a upended five gallon bucket and that seems to work fairly well. (the bucket is sucked down to the bottom). But the suction does not increase at the skimmer. In addition, I see no decrease in the outflow. How can it be that I can effectively cover both bottom drain and skimmer openings and still have outflow? I can't make sense out of it... seems like it has to drawing water from somewhere else in the pool. But where?

    Bob W

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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: Good outflow, low suction...

    What about filter pressure with and without the cleaner attached?

    You only have the skimmer and main drain on the suction side?

    Any air in the pump basket?
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    In the Industry

    Join Date
    Jun 2015
    Wildomar, California

    Re: Good outflow, low suction...

    Maybe try a larger size bath mat to cover the MD.

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    Re: Good outflow, low suction...

    Filter pressure is 20 # with and without...this is after a backwash. Only a skimmer and main drain on the suction side (which is what is making me crazy!)

    There is some air in the pump basket, which has been pretty common since I bought the property 5 years ago.

    I intend to replace the existing filter (sand) with a DE. I am thinking of using the existing pump to test all the lines after i have everything disconnected for the filter replacement. Just use some flex hose to draw straight from pool and then temporarily connect output to both sides and check the flow.

    Bob W

    - - - Updated - - -

    To Old Pool man...

    That is a good idea. that could easily provide a better seal than the upended bucket. Thanks

    Bob W
    Bob W; 30,000 gal inground, about 30 years old
    1 1/2 HP 2 speed pump; single skimmer opening and bottom drain; single ball valve controlling both
    Inground spa; about 400 gallons; 2 HP StaRite pump, Jacuzzi cartridge filter, Hayward propane heater

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