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Thread: Does CYA sink?

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    qbot's Avatar
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    Does CYA sink?

    For reasons I will not get into here, I have no circulation from the main drain. I have just one skimmer and that's how the water circulates.

    When I opened my pool this summer, my CYA level was 50 (pool store test). Since then, every couple days, I stick the vacuum head underwater and pull water from the deep end for circulation. I have not used any pucks since I opened and have strictly stuck to the BBB method. Now my CYA level is ~80 ppm.

    I ask this question as someone who knows nothing about chemistry: Did the CYA sink to the deep end before I started circulating? How else to account for the increase without pucks?

    Anyhow, these are my values. I appreciate any input:

    FC 4.5
    CC .5
    pH 7.6
    TA 100
    CH 260
    CYA 80

    My FC has dropped recently. It was 3 ppm yesterday and I added 2 jugs of bleach. The pool calculator says I'm in my FC target, but the CYA/Chlorine chart says my target should be 9 ppm. Should one be given more weight?
    ~23,000 gal In-Ground Gunite Pool
    Pentair Whisperflo .5 HP Pump
    Pentair Clean & Clear Cartridge (4) Filter

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    Re: Does CYA sink?

    I wouldn't trust a pool store CYA test unless I personally witnessed the entire process, and even then I would have doubts. Firstly because the test is time consuming and the reagent is expensive, providing an incentive to skip the test and say they did it (out of sheer laziness), or even dilute the reagent with water to make it stretch farther. Secondly, because most pool stores promote stabilized chlorine as the holy grail and don't believe/refuse to acknowledge that too much CYA is a real problem. Because of this mindset, they don't think the test is very important, so why bother? The only incentive to test (or pretend to) is to report a low result and hopefully sell you more CYA, stabilized chlorine and pH up, or report an "in range" test so you won't ask them to do it again.
    33' above ground pool, 52" deep, about 27500 g
    sand filter w/zeobrite

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    JasonLion's Avatar
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    Re: Does CYA sink?

    I agree with Miranda, testing errors at the pool store are the most likely cause. Your CYA level has probably been stable, the question is which test is right, if either of them are. With CYA at 80, if your CYA really is 80, you want to keep FC at least at 6 all the time. Aiming for a target of 9 is good.
    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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    Butterfly's Avatar
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    Re: Does CYA sink?

    The best investment we made in our pool was a good test kit! This will put you in control of your pool.

    You can compare recommended test kits here: pool-school/pool_test_kit_comparison

    Many of us use the TF100, link in my sig. duraleigh uses Taylor reagents and has A-1 customer service
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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    qbot's Avatar
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    Re: Does CYA sink?

    Thanks.

    I now have a test kit and have been testing every couple of days. I got the Leslies FAS DPD.
    ~23,000 gal In-Ground Gunite Pool
    Pentair Whisperflo .5 HP Pump
    Pentair Clean & Clear Cartridge (4) Filter

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    Mod Squad Bama Rambler's Avatar
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    Re: Does CYA sink?

    Well now that you have a good test kit how about a full set of numbers? You know we like numbers!
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    qbot's Avatar
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    Re: Does CYA sink?

    The numbers in the OP above are from yesterday. The consensus seems to be that I have to increase my FC. Question: If my FC is currently 4.5 ppm, how much bleach do I need to dump to get a minimum of 6 or target of 9?
    ~23,000 gal In-Ground Gunite Pool
    Pentair Whisperflo .5 HP Pump
    Pentair Clean & Clear Cartridge (4) Filter

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    poolnew-b's Avatar
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    Re: Does CYA sink?

    Quote Originally Posted by qbot
    The numbers in the OP above are from yesterday. The consensus seems to be that I have to increase my FC. Question: If my FC is currently 4.5 ppm, how much bleach do I need to dump to get a minimum of 6 or target of 9?
    Using the pool calculator and assuming your pool is 23,000 gallons as stated in your signature.

    You would need
    1 gallon 2 quarts 3 cups or 2.2 (96 oz) jugs
    to raise it from 4.5 to 9
    Intex Ultra frame 16x48
    Intex 1600GPH Sand Filter
    Taylor K-2005 test kit

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