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Thread: Nine (9) Adjusted Total Alkalinity Questions

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    Nine (9) Adjusted Total Alkalinity Questions

    Q1. I have been reading about Adjusted Total Alkalinity (ATA) concerning Conditioner (CYA), and it seems it's always in reference to Oxidation Reduction Potential (ORP) equipment with a Sensor.

    Q2. If I am not using equipment with an Oxidation Reduction Potential (ORP) Sensor and using only Liquid Chlorine 12.5% and in summer One (1 to 2) 3" Tabs a week, do I still need to Adjust the Total Alkalinity?

    Q3. I also read that you need to Adjust the Total Alkalinity (TA) when the Conditioner (CYA) is at 50 ppm.

    Q4. Would I subtract 1/3 of 50 ppm (16 or17) from the Total Alkalinity (TA)?

    Q5. At what Conditioner (CYA) level do you start subtracting the 1/3 from Total Alkalinity?

    I guess I am confused as to when or when not to subtract 1/3 of Conditioner (CYA) from the Total Alkalinity.

    Liquid Chlorine = 8.0
    pH = 7.6
    Total Alkalinity (TA) = 90
    Conditioner (CYA) = 125 / 3 = 41 or (42)
    Calcium Hardness (CH) = 625 (Customer will not let me dump water)
    Water Temp = 68

    90 - 42 = 48 Adjusted Total Alkalinity (ATA)

    Goal of Total Alkalinity = 110 (110 - 48 = 62 ppm of Sodium Bicarbonate to add)
    Goal of pH = 7.5
    Goal of FC = 8.0 (for southern California summer weather)

    Q6. So, to add 62 ppm, I need to add 10 to 11 lbs of Sodium Bicarbonate to get to my Goal of 110 Total Alkalinity in a 14,400 Gallon Plaster Pool?

    Q7. Also, Since Sodium Bicarbonate raises pH, should I lower the pH to 7.3 before I add the Sodium Bicarbonate?

    Q8. What other Sanitizers are there, that I have to do the 1/3 subtraction with, that have Cyanuric Acid (CYA) in them?

    I couldn't post the calculator picture as I do not have a Flickr account.
    It seems the calculator is telling me that I do not have to add any Sodium Bicarbonate (Baking Soda) I moused over the Fields and nothing showed up.
    Q9. I would think that if the pool is 14,400 Gallons, I would have to add in order to Adjust the Total Alkalinity. Is this correct or did I not do something right with the calculator?
    36k, FNS plus 60 DE filter, in ground cement, 40-60GPM

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

    Re: Nine (9) Adjusted Total Alkalinity Questions

    1) ATA is only useful for calculating the Langelier saturation index (LSI). It has no other purpose.
    2) No one needs ATA, since CSI has replaced LSI.
    3) You need to adjust the TA any time it is out of range. That has only the tiniest relationship to the CYA level, which you might as well ignore.
    4) No, don't try and calculate ATA or use it for any purpose.
    5) You don't. If you were calculating LSI you would always calculate it regardless of CYA level, but there is no reason to calculate LSI.
    6) I get 13 lbs to raise TA by 62 in 14,400 gallons. However, I very much doubt that you want to raise TA by 62 if it is 90 right now.
    7) Sodium Bicarbonate has only a very small effect on PH. If your PH is near the upper limit I would lower it first, otherwise don't worry about it until after the Sodium Bicarbonate has mixed in, then measure PH again and adjust as needed.
    8) CYA is not a sanitizer and there is never any reason to subtract 1/3 of anything from TA.
    9) I don't follow the question. The only reason to raise TA above 90 is if your are using trichlor tablets for chlorine, in which case you should aim for a TA of 120.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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