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Thread: Bottom drain air lock or antifreeze ok?

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    Bottom drain air lock or antifreeze ok?


    I have gone forward and winterized my returns and pump/filter with no problem, but when trying to blow out the main bottom drain, my wet vac doesn't have enough blower pressure to overcome the water pressure of the pool (probably about 6' deep now that it's lowered = 2.6 psi) . I poured about a gallon of pool antifreeze down the drain line, but I can still see the water level slightly below ground when I look down the pipe, so my water/antifreeze mixture is not below frost line. I don't have a valve on the return drain line to airlock, although I suppose I could cut the PVC and add one on.

    Will the water/antifreeze mix be okay or do I need to do something else?


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    Join Date
    Sep 2009
    Greentown, IN

    Re: Bottom drain air lock or antifreeze ok?

    We don't have a shop vac strong enough to blow out the main drain either. We have used antifreeze since we put up our pool and have had no problems. We pour antifreeze into the riser pipe for the main drain until we see the pink of the antifreeze coming out of the drain and then quickly put our cap on to air lock it. I don't believe without a cap or valve it would work as the antrifreeze would work it's way into the rest of the pool water over time.
    Indiana, ABG 24'x52" Galveston by Blue Cascade (Craigslist buy w/part of deck included), 13,500 gallons, Intex SWG, solar panels mix 2, TF-100 test kit.

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    Re: Bottom drain air lock or antifreeze ok?

    So since fall is coming I had to buy a leaf blower, so I got a medium power one with around 390 CFM of air flow (much higher than my wet dry vac). I thought that surely this would blow out the line. Nope. I also installed a valve on the main drain return, so I can now airlock it if I can manage to get the line blown out in another way.

    What if I drilled a hole in the PVC and threaded in a schrader valve? Would charging the drain with compressed air do the trick?

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

    Re: Bottom drain air lock or antifreeze ok?

    That works under most situations. It should displace water to below the frost line.
    Dave J. TFP Moderator
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    Re: Bottom drain air lock or antifreeze ok?

    I'm a little surprised that the pool water valves hold air pressure over an entire winter. Having had experience with vacuum line leaks, I know how hard it is to keep something airtight. I would expect tiny leaks to drain off the pressure over a short time and the line to reflood.

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