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Thread: partial drain/refill technique to lower CYA

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    partial drain/refill technique to lower CYA

    So I am attempting to convert to the BBB method with my pool. The previous owners used trichlor so the CYA is measuring over 100(about 60 with the 1/2 pool 1/2 tap technique). I guess I will go ahead and do a partial drain/refill and I am looking for suggestions on how. I do have an L shaped pool so I was considering putting the hose in the shallow end and draining exclusive from the bottom drain in the deep end.
    Question- will the new water sit on top of the old water or does it depend on the temperature of each? Should I get my chlorine real high and stop the water circulation to attempt this? Is there a better suggestion in general?
    +/-25K gallon L-shape vinyl liner inground
    sand filter
    Taylor FAS-DPD K-2006
    Polaris 360
    junior level BBB

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    JasonLion's Avatar
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    Re: partial drain/refill technique to lower CYA

    I wouldn't worry about the water mixing or not mixing too much, it will still work either way.

    The other option is a little more complex, but uses slightly less total water. That would be by draining 18" and then refilling, and repeating a couple of times. However to do that you need to be able to draw water from only the main drain, otherwise you will lose prime.
    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: partial drain/refill technique to lower CYA

    and when you say "main drain", that's the bottom one?
    +/-25K gallon L-shape vinyl liner inground
    sand filter
    Taylor FAS-DPD K-2006
    Polaris 360
    junior level BBB

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    frustratedpoolmom's Avatar
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    Re: partial drain/refill technique to lower CYA

    Yes
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: partial drain/refill technique to lower CYA

    Quote Originally Posted by JasonLion
    The other option is a little more complex, but uses slightly less total water. That would be by draining 18" and then refilling, and repeating a couple of times. However to do that you need to be able to draw water from only the main drain, otherwise you will lose prime.
    So why out of curiosity would I just do 18" at a time instead of doing it all in one whack?
    +/-25K gallon L-shape vinyl liner inground
    sand filter
    Taylor FAS-DPD K-2006
    Polaris 360
    junior level BBB

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    Mod Squad jblizzle's Avatar
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    Re: partial drain/refill technique to lower CYA

    Because it can be a bad idea to drain a liner pool ... it may shift or be damaged.
    Jason, TFP Moderator
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    Re: partial drain/refill technique to lower CYA

    ok, that makes perfect sense. thanks
    +/-25K gallon L-shape vinyl liner inground
    sand filter
    Taylor FAS-DPD K-2006
    Polaris 360
    junior level BBB

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