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Thread: Should I be concerned with low TA?

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    Should I be concerned with low TA?

    I have an overflow/waterfall in my pool that runs every day. I also try to maintain a lower PH ( 7.2-7.4 ) to help with an ongoing fight against metal stains. This combination of aeration and acid addition causes my Alkalinity to drift downward to 50 without intervention. When this happens, I add enough baking soda to bring it back up to between 70 and 80. I'm not really sure why I am doing this. It's tempting to let the TA stay at 50 because I know the acid demand increases after raising it. Can someone please explain why I want my TA to stay above 70?
    17K gallon IG Plaster. 48sqft Hayward DE filter. Stenner Pump

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    Should I be concerned with low TA?

    If you read the details on PoolSchool, you'll see the primary purpose of maintaining good alkalinity is to act as a pH buffer. This helps prevent wild swings in pH due to acid additions and bather load. It is also very important for maintaining a proper CSI value which determines if your water is corrosive to your plaster or on the verge of calcium scaling.

    Without a good TA value, your water's pH can swing wildly.

    Your water feature is really a secondary issue. Your pool will naturally rise in pH, especially by keeping it so low. The aeration only makes that rise happen a little faster.


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    Mod Squad jblizzle's Avatar
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    Re: Should I be concerned with low TA?

    Try leaving it down at 50-60ppm and see what happens. That would certainly help stabilize the pH as far as not rising so fast.

    Although with low TA, you would likely to maintain a higher pH to help the CSI. The pH rises faster the lower it is ... 7.2 to 7.4 will happen easier/faster than 7.6 to 7.8
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    Re: Should I be concerned with low TA?

    You can keep the TA lower and if you can't have the pH get too high to avoid metal staining then you can increase the Calcium Hardness (CH) to balance the Calcite Saturation Index (CSI).

    A lower TA will slow down the rate of pH rise unless it's due to something like curing plaster if your plaster is fairly new or redone.
    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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    Re: Should I be concerned with low TA?

    Quote Originally Posted by chem geek View Post
    You can keep the TA lower and if you can't have the pH get too high to avoid metal staining then you can increase the Calcium Hardness (CH) to balance the Calcite Saturation Index (CSI).

    A lower TA will slow down the rate of pH rise unless it's due to something like curing plaster if your plaster is fairly new or redone.
    Thanks guys... Here are my latest test results:
    FC: 7
    pH: 7.4
    TA: 70
    CH: 375
    CYA: 40
    Borates: 50
    Temp: 88

    According to PoolMath, my CSI is currently -.12 and will rise to -.32 if I let the TA sink to 50 with everything else unchanged. I wish my plaster was fairly new or redone, but that is not the case. I was nervous about letting my TA remain low, but now that I have I have some expert opinions I plan to stop arbitrarily adding baking soda to stay within the recommended readings. As long as I keep my CSI above -.6 I shouldn't have to worry about damage, right?
    17K gallon IG Plaster. 48sqft Hayward DE filter. Stenner Pump

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    Re: Should I be concerned with low TA?

    If your plaster is well made then the CSI near -0.3 should be no problem, but there is slightly more risk -- but not very much (-0.6 would be more of an issue). If you didn't have the risk of metal stains, you'd target a higher pH. You can always increase your CH level to compensate for the lower TA if you are concerned.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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