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Thread: Drain Pool & Liquid CL but still high CYA

  1. Back To Top    #1

    Drain Pool & Liquid CL but still high CYA

    Inground, Vinyl, 23,000 gallons, pumps run 7X24
    Drain 12" from pool and refilled using well water. Home has a well
    Shocked with 8 gallons of CL

    48 hours later
    FC 2.6 CC 0.6 pH 7.5 Alkalinity 192 Hardness 365
    Vaccummed algae from bottom

    Pool is clearing up, seeing drain, and vac algae of bottom

    What is next
    1. Shock again
    2. Add Liq CL to keep FC and start puks in skimmer

    Can't understand why CYA is so high. Stopped using puks before I drained a few days back
    Inground concrete pool w/vinyl liner
    20' x 40' pool
    Holds 30,000 gallons
    Hayward S220T 22" Sand Filter
    Hayward 1.5HP Super-pump

  2. Back To Top    #2
    what is your CYA level? I don't see it listed... How long had you been using pucks?
    Sometimes a CYA test will read 100 (the highest level on many tests) when the actual value is much higher.

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

  3. Back To Top    #3
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana
    12" of water probably would have dropped your CYA in the neighborhood of 10%. Also, the CYA test isn't very accurate at high levels, so if you thought it was 120ppm, it could have been 150ppm, so draining might not give you a reduction. You'd have to drain half the water out of the pool and replace it to get a 50% reduction in your CYA.

    If you have algae, you should never let your chlorine get down to 2.6ppm. You have to keep a constant high chlorine level. No more than 8 hours between tests, and always add what it takes to get back to shock level for your CYA level.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  4. Back To Top    #4
    Thanks for the help. I drain the pool down to the shallow end (just short of the liner) and refilled. Pool mint green (well water).

    PH 7.6, FC 0, ALK 270?

    CYA better than before but barely reaching the 100 using the Taylor 2006 test kit.

    Shocked with Bioguard Burnout 35 (8 lbs) before nightfall.

    I will check in the AM.

    I will stay away from using pucks. Switch to liq cl and keep it at a high FC.
    Inground concrete pool w/vinyl liner
    20' x 40' pool
    Holds 30,000 gallons
    Hayward S220T 22" Sand Filter
    Hayward 1.5HP Super-pump

  5. Back To Top    #5

    Join Date
    Apr 2007
    Are you using a metal sequestreant since you have well water?

    14,000 gallon, in ground, plaster, free form, play pool.
    Sta-Rite Max-E-Glass with a 1.5 hp Emerson motor
    WaterCo Micron High Rate sand filter S750 490 lb, 4883 sq ft - using ZeoBest
    In floor Polaris cleaning system
    Blue Diamond robot for those after storm days when I can't wait overnight for the in floor to clean it.

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