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Thread: alkalinity

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    i have a 30,000 gallon inground pool- approximately 6 years old. i havent had any real main concerns until recently.
    at the end of 2012, my cya was over 100, so i quit using sticks and chlorinated with bleach only. well this year, upon opening, i'm told (by pool store) that my cya is still over 100 (my taylor test reads 70) and that i need to drain my pool. i guess i'm confused as to how it's still that high, even though i havent used any stabilized chlorine and drained almost half the pool before closing in 2012?
    do i really need to drain the pool? also, the pool store is saying my TA is low (due to cya)......
    my readings:
    FC: 3.5
    CC: 0
    PH: 7.4
    TA: 110
    CH: 210
    CYA: 70
    borates: 50

    pool store readings:
    FC: 3.5
    CC: 0
    PH: 7.4
    TA: 102
    ATA: 69
    CH: 218
    CYA: 100

  2. Back To Top    #2
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: alkalinity

    Welcome to TFP!

    Trust your own readings. The CYA test isn't accurate at extreme levels, so a reading of 100ppm could actually be 200ppm or more.

    Your TA is fine.

    Your only real issue is that you should maintain a higher chlorine level with your CYA at 70ppm. You should follow the Chlorine CYA Chart
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  3. Back To Top    #3

    Re: alkalinity

    thank you for your response!!
    so what you're saying is: i dont need to factor in the high cya reading when testing for alkalinity? and i dont need to drain my pool? the pool store wants me to add 10 lbs of alkalinity increaser and is making me feel like my own cya reading is wrong. (i purchased the "dummy" solution and practiced doing the test, so i'm fairly confident in my findings).
    also, how high should i maintain my FC levels until the cya is at a more appropriate level?

  4. Back To Top    #4

    Re: alkalinity

    sorry- i just saw the chlorine cya chart you posted....duh!

    thank you for your help!

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: alkalinity

    Don't do the CYA correction to TA. Around here we always use the TA number directly from the test kit. The adjusted TA value only matters if you need it to use the outdated way of calculating your saturation index, and there isn't even any reason you would need to know the saturation index.
    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

  6. Back To Top    #6

    Re: alkalinity

    awesome!!! i appreciate your advice!!!!

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