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Thread: Setting CH goal with low TA and rising PH

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    BattleOfYakima's Avatar
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    Setting CH goal with low TA and rising PH

    17-20k gallons, absolutely crystal clear, still a couple black algae dots under the de-laminated/bulging plaster, but everything brush-able has long been killed.

    FC 9
    CC 0
    PH 7.4 (1 drop to 7.2, 2 drops to 7.0)
    TA 60
    CYA 50 (rounded up from just under)
    CH 200

    Old, pitted, some de-laminating plaster pool. High usage, high oil/lotion, high environmental debris, & heavy summer rains coming. Regular MA additions. Totally exposed to central Florida sun.

    I have my calcium arriving tomorrow. I know it will not be working any miracles, that's fine. I just want to take better care of this plaster until it is redone in the future.

    I plan on dropping PH to 7.2 today before the CH addition tomorrow to minimize clouding.

    I was playing with PoolMath and it seemed like pushing my CH up to around 500 gives me a much better cushion to stay closer to 0 in the CSI, especially when PH is at 7.2, which is where I usually drop it to when I add MA.

    Also, I pushed my TA down from 120 to 80 during last summer to help reduce the MA additions, and it really worked wonders. Much less MA used and much less PH rise throughout the week. Should I keep TA at 60 or bump back up to 80?

    Lastly, this is my first summer ever with this pool having a CYA under 100++ and I'm greatly enjoying being able to test PH without having to dip under the high target FC, which I treat as my minimum FC given the unpredictable rain/bathers, but wondering if I should bump CYA up to 60 from 50 which still lets me test PH without jeopardizing the FC. I've read there is a +/- 15 so that's why I'm asking instead of just doing it.

    Thanks for all answers/thoughts.
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    Mod Squad Texas Splash's Avatar
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    Re: Setting CH goal with low TA and rising PH

    Since you realize the current plaster will require repair later, best you can do is simply try to maintain a healthy CSI level - close to neutral or a little above. You're only barely under the recommended minimum CH of 250, so you won't need to add much. But even if you elect to go up to only 300, that will still work as long as you let the pH and TA remain a little higher. Pulling pH down to 7.2 is a little more corrosive that you probably need at this time.

    For example: A pH of 7.7, TA of 80, and CH of 250 gives you a CSI of about 0.04 which is very good. If you increased the CH to 500 in that same example, the CSI would increase to about 0.28 which in your case won't hurt you either. In either case though, I would avoid a pH of 7.2 as that one item alone pulls your CSI down under zero (in the negative), and you don't need a negative CSI with plaster already peeling-off.

    I think if I were you, I would increase CH a little at a time to avoid the cloudiness you're concerned with and focus more on keeping pH between 7.6-7.8, and TA around 80 or so. Hopefully find that balance on the upper end where pH can remain stable there. Over time, increase CH a little at a time and monitor since in FL you may experience lots of water exchange from heavy rains. Use the Poolmath calculator often to monitor the CSI level and try to keep it above zero to avoid any further corrosion.

    As for the CYA, You could increase it slightly, but only if you feel that the sun is steeling too much FC each day - more than 3-4 ppm. Otherwise, just let it ride for now and monitor. Your call though. Hope that helps.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Setting CH goal with low TA and rising PH

    Thank you very much! I understood everything and will make the necessary adjustments. Thank you especially for pointing out that it is advantageous at this point to leave my PH 7.6-7.8.
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    Re: Setting CH goal with low TA and rising PH

    TA 60 --> 80
    CH 200 --> 425
    CSI right above or below 0.0 depending on temperature
    Thanks!
    FYI The Snow Joe Professional 94% 94% Pure CaCl2/calcium chloride Pellets, poured slowly in front of the return that points to the deep end, mostly dissolve on the way down to the bottom, and a one pass brushing 30 seconds later was enough to completely dissolve. Testing 1 hour later, circulation on, was the same as the next day, using 10ml sample size.
    At time of addition, PH 7.5 TA 80, FC 6, CYA 50
    No clouding at all!
    An hour later I brought FC up to 20 to see if it would cloud, out of curiosity, and it did not. Lucky me!
    Could be upped TA, increased pump run time, wind conditions/direction, better time of day, or boosted FC, but today's sparkle is even more brilliant. No complaints here.

    Thanks for help. Now my plaster will last as long as it can and I'm not going to worry about it ever again until replacement time.
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    Mod Squad Texas Splash's Avatar
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    Re: Setting CH goal with low TA and rising PH

    Sounds like you've got a handle on things. Enjoy your weekend.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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