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Thread: high cya

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    high cya

    Hi everyone,

    I've just started doing my own chemicals and need help. I have a vinyl-lined 29,000 gal pool, SWG. Have had a SWG x 2 yrs. Just got a new cell; old one never really read things correctly.

    My chemicals have been off for a month. Today, ph 7.1, FC 0.5, CC 0.5, T/A 100, CYA 110.

    I've used the pool calculator, but was trying to avoid draining the pool.

    Per the calculator, I've added dichlor daily for the past 2 weeks to get FC up daily. I'm not sure if I should shock, or to drain to lower CYA. What problems result from elevated CYA?
    18x36, 29,100 gal vinyl-lined pool
    SWG, Pentair FNS Plus filter
    TF100 test kit, pool calculator

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    Mod Squad woodyp's Avatar
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    Re: high cya

    Biggest problems are having to maintain a much higher level of FC in the pool to achieve the same results at a lower cya value. See the chlorine/cya chart in pool school to see how much those shock values have to be at high levels to kill off "problems".
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
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    Re: high cya

    Welcome to TFP!

    Two quick questions -- first, how did you get your test results, I assume its a pool store reading. The pool stores are notoriously bad at measuring CYA, so their reading of 110 may be much higher.

    Second, how does your water look?

    Let us know and we can figure out a plan. Unfortunately CYA doesn't go away by itself, so a partial drain may be in order.
    28K, 20' x 40' IG - Vinyl Liner, Hayward DE Filter, 1.5HP Pump, 250K Hayward BTU Heater, Aquabot Breeze 4WD robotic cleaner

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    duraleigh's Avatar
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    Re: high cya

    Welcome to the forum
    I've added dichlor daily for the past 2 weeks to get FC up daily.
    1. Stop using dichlor....that's what's caused your CYA to be high.

    2. Put Clorox in your pool to get your FC up......the pool calculator will tell you how much you need to elevate your FC to about 10ppm.

    3. Reduce your CYA down to 50ppm by a series of partial drain and refills.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Butterfly's Avatar
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    Re: high cya

    Quote Originally Posted by mabmango1@gmail.com
    Hi everyone,

    I've just started doing my own chemicals and need help. I have a vinyl-lined 29,000 gal pool, SWG. Have had a SWG x 2 yrs. Just got a new cell; old one never really read things correctly.

    My chemicals have been off for a month. Today, ph 7.1, FC 0.5, CC 0.5, T/A 100, CYA 110.


    I've used the pool calculator, but was trying to avoid draining the pool.
    The problem with CYA tests is that they are accurate up to 100 and can read anything over 100 as 100. Is your CYA test of 110 a result of a dilution test? You can dilute your pool sample with half pool water and half tap water and double the test results. Less accuracy, but you would know if it is closer to 100 or 200.

    Per the calculator, I've added dichlor daily for the past 2 weeks to get FC up daily. I'm not sure if I should shock, or to drain to lower CYA. What problems result from elevated CYA?
    As mentioned, it is difficult to maintain a pool with that high a CYA. Shocking the pool to that level of CYA would be expensive and difficult. And, as Dave said, the dichlor is what increased your CYA. Any time you need extra chlorine beyond what the SWG can produce or if you need to shock, use liquid chlorine/bleach because it has less/no side effects.

    Recommended CYA levels for SWG's is 60 to 80. See 'water balance for swg's in Pool School.
    pool-school/water_balance_saltwater_generator

    I suggest you do the drain/refill dance and lower the CYA to about 80.
    Then retest and adjust from there.

    It would be helpful if you add your pool and equipment specs in your sig.
    Go to User Control Panel (top left under TFP logo) select Profile, then Edit Sig.
    This will help folks help you

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    Re: high cya

    Im testing with a home kit - TF-100 I got thru this site. So I used the CYA view tube and all. I was wondering if the dichlor was the reason. Has it always raised CYA? Any suggestions on how many inches/feet to drain if this is the case?
    18x36, 29,100 gal vinyl-lined pool
    SWG, Pentair FNS Plus filter
    TF100 test kit, pool calculator

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    Re: high cya

    Pool Calculator will tell you, enter current CYA and goal, with correct volume of pool.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Richard320's Avatar
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    Re: high cya

    Quote Originally Posted by mabmango1@gmail.com
    Im testing with a home kit - TF-100 I got thru this site. So I used the CYA view tube and all. I was wondering if the dichlor was the reason. Has it always raised CYA? Any suggestions on how many inches/feet to drain if this is the case?
    Yes, dichlor is the reason. Every ounce you added, added more CYA.

    The easiest way to figure out how much to drain is to pick a target. Then figure out what percentage that is. say you want 70; you're at 110. 70/110 is 63%. So you need to drain 37% of the water. But how much is that? If you can figure out your average depth, it's easy. My pool average depth is 60 inches - yours will be different - so if I want to lose 37%, I'd pump out 22 inches. .37*60.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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