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Thread: Draining a pool

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    Draining a pool

    Hello all -

    I need to drain my pool to do some repairs under the liner. I'm trying to figure out how long it will take to drain the pool.

    I have a Waterway 2 hp high flow pump. That said, it shows 150 gpm at 5ft of head. Am I correct in the following logic? I'm going to put this pump on the pool deck. I'll attache a hose to the intake and put it into the pool, which is about 4 feet deep. Then run the discharge hose off the deck, across the patio and down the driveway. The only real head involved is the 54" pool wall height. So, can I expect a little less, say 130-140 gpm?

    Then since the pool is 15 x 30 and it's only filled to the return at this point, because it's in winter mode, there is roughly 48" of water in the pool. This works out to roughly 9,293 gallons. So, 9,293 gallons / 130gpm = 72 minutes to drain the pool or around 1hr 10 mins. Is this about right? sounds really fast to drain the pool.


    Thoughts?

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    JasonLion's Avatar
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    Re: Draining a pool

    The "head" listed for the pump is dynamic head, it includes both the static height difference and the friction of trying to push the water through the pipe. The static height difference is between the top of the pool water and the outlet of the hose. If you keep the hose outlet below the bottom of the pool this will actually be negative. The friction of pushing water through the hose depends on what size and kind of hose/pipe you have. For a garden hose it is going to be substantial, for a 4" rigid hose it will be minimal.

    Unless you use some large diameter hose, 2+" for example, the total time is likely to be much more than you estimated.

    Also, how old is your liner? If the liner is 5 years old or older, chances are it will not be reusable after you drain the pool. In the first year or two the liner will almost always be fine. Between 2 and 5 years old the risks of ripping the liner go up. 5 years old or older and chances are the liner won't survive.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Join Date
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    Re: Draining a pool

    Also keep in mind that the water needs somewhere to go. 9,000 gallons is a LOT of water. When I drained our pool a couple of summers ago I ended up making a manifold for the output of the pump that let me attach 4 garden hoses so that I could spread the water around our 1.1 acre lot. Just dumping into the backyard was flooding the neighbors lawn and driveway.
    26,000 Gallon Gunnite IGP
    2 HP Challenger High Head Pump
    60sf Nautilus DE filter
    Polaris 280

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    Re: Draining a pool

    Jason,

    Thanks. The liner is 2 yrs old. I hope to do a quick repair and reinstall it. I'm hoping within a couple of hours.

    My plan now is to use pool vac hose for both the intake and discharge. When you say significantly more time, are we talking 3 hrs to drain the pool or 6 hrs? My concern is having enough time to do the repairs once the pool is empty. I figure I can start emptying the pool at around 7:00 and start working around 10:00. This would give me 9 hrs to do the repair and get the liner back in before it starts to get dark.

    Is 3 hrs a reasonable estimate to empty the pool?

    Thanks.

  5. Back To Top    #5
    JasonLion's Avatar
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    Re: Draining a pool

    3 hours sounds reasonable. Use a hose that is as short as possible (if you have a choice) and make sure the outlet is below the bottom of the pool (if possible).
    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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    Re: Draining a pool

    Jason,

    Thanks!! I have an old hose I can trim to length and use for the intake. I'll let you know how it goes.


    Regards,
    Rich

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    Re: Draining a pool

    In some areas there are rules about where to dump the water. Where I am, when you drain it must go into the sewer, not the ground/street/storm drain. Your water dept should be able to tell you.
    --paulr
    BBB "Intermediate Swimmer"
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    guamguy's Avatar
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    Re: Draining a pool

    Do you have a DE or sand filter with a mutiport valve? If so, you could use that as well as your Waterway pump to really speed things up
    12,800 gallon IG plaster kidney-shaped pool, waterslide, 800 gallon spa.
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