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Thread: Can't keep TA high enough

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    eemueller's Avatar
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    Can't keep TA high enough

    I haven't been having any trouble with my water chemistry, until recently. In the last couple of weeks, I can't keep the TA at 70. It wants to drop. I will add baking soda to drive it up, get the pH back to 7.5, and then within a few days the TA is headed down again. It stabilizes around 30. I'm not sure why this has started to happen, or how to stop it. Thanks for any advise.
    Eric
    32K gal rectangular pebble sheen IG salt pool, 1200 gal pebble sheen IG salt spa
    Jandy AquaPure 1400 SWG, Jandy AquaPure 700 SWG
    Sta-Rite 2HP pump, Sta-Rite 1HP pump
    Triton II sand filters on both, Pentair MasterTemp 400K BTU nat gas heater
    CAT 1000 pH controllers w/ Stenner acid pumps on both, Levolor auto-fillers on both

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    Mod Squad jblizzle's Avatar
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    Re: Can't keep TA high enough

    How are you adding chlorine to your pool?
    Jason, TFP Moderator
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    Re: Can't keep TA high enough

    The acid pump is the likely cause. What pH do you have the pH controller set for?

    What is the TA of the fill water?

    Note: It's a salt system.

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    eemueller's Avatar
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    Re: Can't keep TA high enough

    It is a salt pool. I keep the pH controller set at 7.5 and it hardly ever varies. The pH of the fill water is about 7.7-7.8. I've used my Taylor test kit to confirm what the CAT controller is showing for pH, and it checks out fine. I'm stumped.
    32K gal rectangular pebble sheen IG salt pool, 1200 gal pebble sheen IG salt spa
    Jandy AquaPure 1400 SWG, Jandy AquaPure 700 SWG
    Sta-Rite 2HP pump, Sta-Rite 1HP pump
    Triton II sand filters on both, Pentair MasterTemp 400K BTU nat gas heater
    CAT 1000 pH controllers w/ Stenner acid pumps on both, Levolor auto-fillers on both

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    Mod Squad jblizzle's Avatar
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    Re: Can't keep TA high enough

    How much acid are you generally adding? You may find that the pH is more stable with less acid (and thus a more stable TA) if you set it up higher like 7.7
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    eemueller's Avatar
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    Re: Can't keep TA high enough

    What's so weird is this just started in the last couple of weeks. All summer, it was fine. Can lower nighttime temps have anything to do with it? We're not really swimming anymore, and the water temp is down to around 70.
    32K gal rectangular pebble sheen IG salt pool, 1200 gal pebble sheen IG salt spa
    Jandy AquaPure 1400 SWG, Jandy AquaPure 700 SWG
    Sta-Rite 2HP pump, Sta-Rite 1HP pump
    Triton II sand filters on both, Pentair MasterTemp 400K BTU nat gas heater
    CAT 1000 pH controllers w/ Stenner acid pumps on both, Levolor auto-fillers on both

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    Re: Can't keep TA high enough

    If you're getting extra aeration, then the pH will go up due to carbon dioxide off gassing. Then, the acid pump turns on and the pH and TA go down. This is the basis of the lowering TA (Total Alkalinity) procedure.

    Then when you add bicarb to raise the TA, the process starts all over. It's an endless cycle.

    The way to break the cycle is to maintain a lower TA (50 to 60)
    and a higher pH (7.7 to 7.8) to lower the amount of carbon dioxide in the water.

    You should also maintain the CYA (Cyanuric Acid) at 60 to 80 ppm, and the CH (Calcium Hardness) high enough to reduce the risk of dissolving calcium carbonate out of the plaster.

    Another possibility is a leak and the auto fill introducing a lot of fresh water. You should verify if the auto fillers are adding a lot of water.

    Adding Borates can help, but I would wait to see what you can resolve without them first.

    Can you post a full set of readings, and the TA of your fill water?

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