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Thread: Pump won't prime after halfway draining pool

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    Pump won't prime after halfway draining pool

    I'm in the process of draining my water level below my light to do some maintenance on it. I'm using my pool pump to drain it, taking water only from the main drain and suction side vacuum line (both skimmers are turned off via diverter valve). Everything was going fine but I decided to give my pump a break, so I turned it off. A couple hours later I turned it back on but there was no prime. I tried to manually prime the pump via water hose in the pump basket. When I turn on the pump, it'll suck in the water in the basket but nothing else, no prime. I then put a hose in one of the skimmers and opened up the diverter but no change.

    So the only thing that's changed from my normal pool operation is that the water level is below the skimmers, which is why they're off via the diverter. Since the water is below the skimmers, and it won't prime, am I correct in thinking that air is probably getting in through one of the skimmers causing the lack of prime? Like I said above, everything was working fine until I turned off the pump then tried to turn it back on. Is it possible that the leak is small enough that it didn't lose prime while it was running but once I shut it off and tried to turn it back on, that it's letting enough air in to not start a prime?
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    dumbcluck's Avatar
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    Re: Pump won't prime after halfway draining pool

    I know this doesn't answer your question but why would you drain the pool to service the light? It's designed to pull out of the water onto the deck for such purposes.
    -Jimbo- My pool was full of dirt and trees. Now it's full of water and children!
    20k gallon inground pool, 18" raised spa 7' round, 8 jets, 3" spa plumbing. Pentair intelliflo 3hp vsp, Easy touch 4 w/ ic 40, CCP 420 cartridge filter, Raypak 407a w/ cupro nickel, Screen logic 2, Pentair intelliph, spa side remote, Pentair 5g color lights pool and spa, TF-100 test kit with speed stir and Dolphin Oasis Z5

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    Re: Pump won't prime after halfway draining pool

    I'm plugging the hole in the light conduit because that's causing a slow leak in the pool. Nothing to do with the light itself.
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    Re: Pump won't prime after halfway draining pool

    The lowered water level has likely increased the "suction" required to pull the water from the pool water level to the pump. Your pump is simply not strong enough to lift the water that much higher.

    If that's the case, I know of no easy fix. YOu don't happen to have a spigot on the pressure side of your system, do you?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Pump won't prime after halfway draining pool

    Quote Originally Posted by duraleigh View Post
    The lowered water level has likely increased the "suction" required to pull the water from the pool water level to the pump. Your pump is simply not strong enough to lift the water that much higher.

    If that's the case, I know of no easy fix. YOu don't happen to have a spigot on the pressure side of your system, do you?
    This was my fear but didn't know if it was possible. I wasn't sure how much the weight of the water itself helped pull it through the suction lines. No spigot that I know of.
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    Re: Pump won't prime after halfway draining pool

    I wasn't sure how much the weight of the water itself helped pull it through the suction lines.
    The pump must create an area of low pressure to allow the water to be lifted up into your pipes and pump. It is pretty significant.

    Pumps like to "push" water but they do not like to "suck" air.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    mas985's Avatar
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    Re: Pump won't prime after halfway draining pool

    Theoretically, most residential pool pumps should be able to prime up to 8' or so but it usually requires some help like priming valves on the suction line and completely air leak free. This allows you to fully fill the pump basket with water which in turn helps develop low enough pressure in the pump basket so atmospheric pressure can push water up the pipe.

    But if you are trying to empty a pool, you really shouldn't stop the pump because it is so hard to re-prime. However, even doing that doesn't guarantee that you will be able to empty a pool. As the water level drops, suction in the pump basket increases and the pump lid gaskets are more likely to leak air not to mention other parts of the plumbing so in a lot of cases, the pump will lose prime anyway.

    Dave, isn't your pool that requires a high lift when priming?
    Mark
    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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    Re: Pump won't prime after halfway draining pool

    Dave, isn't your pool that requires a high lift when priming?
    Yes! (good memory). I have never shot it with a level but I would say it is about 6 - 6.5 feet and a real bear to prime if I lose it.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Pump won't prime after halfway draining pool

    If I was you at this point is to rent a pump w a 3 to 4 inch line and finish your job vs trying to deal w loss of prime at this point. Prob $60-$80 per day


    13000 gallon pool, SWG, DE Filter, 2 sheer descent waterfalls, built Jan 2014

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    Re: Pump won't prime after halfway draining pool

    In some cases, you can set up a siphon to drain the pool. If you have a spot lower than the level you're trying to drain to, then you could set up a siphon. You could try plugging the skimmers to see if that allows you to restart the pump. Or you could by a small submersible pump to finish the drain.

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    Re: Pump won't prime after halfway draining pool

    I ended up buying a 0.5 hp pump from Home Depot. It's taking forever, but it's working.
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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