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Thread: How to make an underdrain

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    How to make an underdrain

    Or sump, or pump-out, or whatever it's called - the pipe buried in gravel under the deep end of a pool which lets you pump out the ground water so the vinyl liner can be changed.

    I'm pretty sure that the way my PB made one was to fasten some kind of plastic screen cloth over the end of a length of pipe and bury it in 3/4 washed gravel under the deep end. The gravel seems fine, but after some googling I'm worried about clogs. Should I ask him to dig it out and either drill holes or cut slits along more of the buried length to ensure that one misplaced chunk of clay can't render it useless? If he won't, is there any grave risk in going down there and doing it myself (after telling him I will, obviously)?

    Thanks,

    Sim
    Hydraulically mundane 20x40 rectangular polymer (~30K gal.), IntelliFlo VS+SVRS pump, IntelliChlor IC40 SWCG, Pentair CCP520 cartridge filter, LED light, 2xDeck Jets, SR Smith Turbo Twister slide

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    Re: How to make an underdrain

    What kind of pipe? PVC? 4" corrugated?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: How to make an underdrain

    1.5" flex pipe. Maybe 2"? I'll check when it's light.
    Hydraulically mundane 20x40 rectangular polymer (~30K gal.), IntelliFlo VS+SVRS pump, IntelliChlor IC40 SWCG, Pentair CCP520 cartridge filter, LED light, 2xDeck Jets, SR Smith Turbo Twister slide

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    Re: How to make an underdrain

    Hmmm. Well, if it's for the purpose of draining off water, he would've done much better with 4" corrugated and slit black poly pipe. Encased in 3/4 or 1" gravel and leading to a sump, it's about as good of a drain system (in this case) as can be made.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: How to make an underdrain

    He's using 4" corrugated slit black poly for the curtain drain "run to daylight", so there should be some extra. How would you connect this to the sump line? I assume the sump should be 1.5" or 2" pipe.
    Hydraulically mundane 20x40 rectangular polymer (~30K gal.), IntelliFlo VS+SVRS pump, IntelliChlor IC40 SWCG, Pentair CCP520 cartridge filter, LED light, 2xDeck Jets, SR Smith Turbo Twister slide

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    Re: How to make an underdrain

    We're not quite on the same page. I envision the black corrugated pipe leading to an underground sump or catch basin.

    An 8" PVC pipe is then inserted vertically down into that catch basin forming a wellpoint. During high water, a submersible pump can be lowered down the wellpoint to with draw all the water that accumulates in the underground catch basin (sump)
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  7. Back To Top    #7

    Re: How to make an underdrain

    What my PB did was to bury one end of a 1.5" pipe capped with a foot valve (or cheap imitation thereof) in 12" or so of gravel below the deep end. It runs along the contour of the hopper floor to the surface, where it's connected to a pump and used to evacuate seepage during construction. Afterward, it will be capped and left in place.

    In my extremely sandy soil, it may be that the basin isn't necessary. I'm just worried that there's not much exposed area at the end of the pipe, and it would be easy to clog it.
    Hydraulically mundane 20x40 rectangular polymer (~30K gal.), IntelliFlo VS+SVRS pump, IntelliChlor IC40 SWCG, Pentair CCP520 cartridge filter, LED light, 2xDeck Jets, SR Smith Turbo Twister slide

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    Ohm_Boy's Avatar
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    Re: How to make an underdrain

    It could be a well point.
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

  9. Back To Top    #9

    Re: How to make an underdrain

    Oops. I checked with the builder, and he did drill holes along the length of the buried pipe before covering it with heavy plastic screen.
    Hydraulically mundane 20x40 rectangular polymer (~30K gal.), IntelliFlo VS+SVRS pump, IntelliChlor IC40 SWCG, Pentair CCP520 cartridge filter, LED light, 2xDeck Jets, SR Smith Turbo Twister slide

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