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Thread: Chemistry Advice on TA and CH

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    Join Date
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    Chemistry Advice on TA and CH

    I just bought a house and inherited a salt pool with poor chemistery.

    FC = 9 (was as high as 11)
    CYA = 40
    pH = 7.5
    TA = 110
    CH = 280
    Salt = 3200

    I am in the process of raising the CYA to around 80. pH was too high originally at over 8 so I quickly lowered it to 7.5 with acid. I am lowering the Aqua Rite SWG % output to get to FC of 6. Right now, TA is too high and CH is too low. But are these two levels a concern? It would seem so (for TA) based on the notes I read of TFP in the SWG section. Thank you for hte advice.
    10000 IG plaster pool / Pentair Clean & Clear Plus 420 sqqft cartridge filter / Aqua Rite SWG T-15/ Taylor K-2006 Test Kit

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    mas985's Avatar
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    Re: Chemistry Advice on TA and CH

    CSI is about perfect for a SWG pool so I wouldn't change a thing. It is the combination of PH, TA and CH that matters more to scaling and corrosion than the individual components although you shouldn't let any one component get too far out of range. Plus, if you have hard fill water, CH may climb over time anyway and then you will need to bring down TA some.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Mod Squad pooldv's Avatar
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    Re: Chemistry Advice on TA and CH

    With TA at 110 your PH will probably tend to rise. Adding acid to lower PH back to 7.5 or so will slowly lower your TA. It is important to keep PH at 7.8 or lower.

    More on lowering TA here, Pool School - Lower Total Alkalinity

    More on basic pool chemistry here, Pool School - ABCs of Pool Water Chemistry

    More on saltwater pool chemistry here, Pool School - Water Balance for SWGs
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    Re: Chemistry Advice on TA and CH

    If you are lucky enough to find your pool's pH being stable at the current TA, then of course there's no need to change it. If you do find the pH to rise over time too quickly for you, then you can add acid which will lower both the pH and over time the TA should drop (unless you've got a lot of evaporation and refill). If the TA drops over time, you can target a higher pH (say 7.7) if that becomes more stable.

    Basically, if it ain't broke, don't fix it, so just see how your pH goes. It's possible it's OK where it is though that would be unusual for an SWCG pool.
    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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    mas985's Avatar
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    Re: Chemistry Advice on TA and CH

    Also, if you were to target a low PH of 7.2, post acid dosing, it would keep your CSI around -0.5 which would help keep scale off the SWG plates and it would also slowly drop TA. I just think adding CH to an SWG pool is unnecessary unless it is really low (<200 ppm). CH is usually hard to keep down for most people so I think it is much better to manage PH and TA to keep CSI in check.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Chemistry Advice on TA and CH

    Thank you all for the advice.
    10000 IG plaster pool / Pentair Clean & Clear Plus 420 sqqft cartridge filter / Aqua Rite SWG T-15/ Taylor K-2006 Test Kit

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