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Thread: Is high CYA a problem if pool looks clean and clear

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    Join Date
    Sep 2010
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    Is high CYA a problem if pool looks clean and clear

    I have an inground 12,700 gallon vinyl-liner pool near Sacramento, California. For the past couple years I have used pucks and bags of shock, and this summer I developed a bad algae problem that took about 2 weeks to clear up with constant brushing, vacuuming, backwashing, running the filter and adding bags of shock. The pool is now algae-free and looks great, sparkling and clearer than ever. Last week I found the troublefreepool website (which is wonderful) and I have just switched to BBB. The pool still looks great but I am concerned about the CYA level being really high. Will the CYA level eventually go down on its own, and if so, how long will that take through normal evaporation and backwashing? Should I even bother with draining or partial draining if the water looks so great? I would have to get a permit from my City to drain and that would be a hassle. Here are my most recent test levels:

    FC 1.0
    pH 7.5
    TA 100
    CH 85
    CYA >100 (probably around 150 but the test kit is only marked to 100)
    Sacramento California

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    dmanb2b's Avatar
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    Apr 2009
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    Re: Is high CYA a problem if pool looks clean and clear

    Welcome to TFP

    How are you testing CYA? If it is in fact over 100, you can dilute your pool water 50% with tap water and retest...multiply the result by 2. You're FC of 1 is way too low for the CYA level. I know there are some folks on here you have successfully managed pools with high CYA, but if it is in fact that high and draining is not an option, then you FC should never be below 7ppm.

    CYA will come down over time with significant rainfall and backwashing, but evaporation does not reduce CYA. Evap actually increases your CYA level until you add the water back that was lost in the process.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: Is high CYA a problem if pool looks clean and clear

    Thanks for the reply. I did another CYA test with 50% tap water, and the test showed about 82, so that would be CYA of 164. I guess I will need to start doing several partial drains... what a pain! But it beats the amount of bleach I would need to buy otherwise.
    Sacramento California

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    Re: Is high CYA a problem if pool looks clean and clear

    Since you are nearing the end of the season - except for this current blast of heat - you might want to consider not adding any more dry shocks, and let winter rain dilution help you out before you decide to D&F.
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    Re: Is high CYA a problem if pool looks clean and clear

    With the water temps cooling off and the high level of CYA in the water, the chlorine usage will be rather low so while it will take an initial larger amount of bleach to raise the FC level, it should hold reasonably well and not need very much to maintain, unless nascent not-yet-visible algae growth has already started.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Richard320's Avatar
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    Re: Is high CYA a problem if pool looks clean and clear

    It's liveable, I've been doing it for almost a year now.

    I started at about 220 - but who really knows when it's diluted 1:3? With pumpouts and rainwater dilution, it got down to about 140 for months. Calcium Saturation was getting critical, so I was forced to drain and refill some, which also lowered CYA. For the past few weeks, I've been down to double digit CYA.

    You will have to maintain much higher FC with high CYA. Higher than you can read with the color match test. The FAS-DPD test will do it. It's available seperately or as part of the TF100 kit, or the Taylor K2006. All available from http://tftestkits.net. If you get the full kit, get the XL. It comes iwth double the reagents. Otherwise, get two. You'll be using a lot of the stuff.

    Your chlorine consumption will not be any greater than someone with normal levels. But your minimum will have to be higher. The reactive - I'm sure there's a better term, but I don't know it - chlorine is no stronger than someone running 1 or 2 and no CYA. No smell, no dry skin, no burning eyes, no faded swimsuits.

    We're near the end of the season; I'd hold off on pumping until the rains start.

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