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Thread: Is TA of 200 too high when PH is stable?

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    Is TA of 200 too high when PH is stable?

    Long story related to CYA way over 100 all of last year due to years of puck usage by previous owner, even after draining and replacing ~1/3 of the water, 2+ PPM of iron and TA of ~240 all of last year, resulted in draining and replacing ~98%+ of the water last week after using AA to remove rust staining. Since my well water has 5 PPM of iron, TA = 450 hard and TA = 550 when softened, I used lake water to replace the pool water. I had tested it at TA 180 out of the lake, but it's currently closer to 200 in the pool.

    All of last year the PH was actually quite stable given the high TA and I never had to adjust it as it was steady at around 7.5 - 7.8.

    Current test results

    TA = 200
    CH = 150
    CL = 3.5 (still coming down from slamming to 12 after filling with lake water)
    CC = < 0.5
    PH = 7.2 The Iron unfortunately is just under 1 PPM even from the lake, so figured it's better to leave the PH lower, and it's been steady for a week, even with the high TA.
    CYA = < 10

    I'm not concerned about the CYA at this point as the pool is lightly used and has an automatic cover so there's little CL loss to sunlight. I can bring it up over time if I decide to do so with pucks while on vacation, etc. CH is fine as I have a fiberglass pool that doesn't have any calcium in the gelcoat, so I don't really want to raise it. Less chance of lime deposits with lower hardness.

    The pool is looking very good now after a week of 24 hour a day filtering. It was very green to start with, I assume from algae in the lake water, but it's been killed and removed, and other than some debris that's settled on the bottom that I need to vac again, it's nice and clean.

    Due to the automatic cover I'm not keen on using acid to lower TA and aerating to raise it back up again, primarily because I don't live there and don't like leaving the cover open with no one around. There's no fence around the pool, so it's not a good idea from a liability standpoint.

    In addition, I tried this last year with almost no success. I aerated for 3+ days for 24 hours continuously with the cover partially open, and the PH @ ~7.0, and the PH would not come up after dropping it with acid and days of aeration. I finally gave up and put Borax in to raise it up again, and let it go. Interestingly enough, the rest of the summer I never had to add either acid or Borax to adjust PH again and it remained steady where I adjusted it. I made an aerator with PVC pipe and holes drilled in a cap to bring it up above the water and spray back down into the water. It created lots of foam, but didn't do squat for the PH.

    I'm a bit anal, and I would prefer the TA to be ~100, but I'm not sure I can get there, plus with 550 TA from the softener, anytime I add additional water it will drive it up again. I most definitely won't be using hard water to refill due to the high iron content. I would also like to use Boric Acid to Borate the pool, but I understand that it's important to adjust the TA first, assuming I can get it adjusted. However, if aerating won't bring up the PH, it becomes a matter of using acid to lower the PH & TA and using Borax to raise the PH again. However, I'm not sure that this will even bring the TA down while maintaining an appropriate PH level.

    Given all the above, how important is it to try to lower the TA?
    21,000 gallon, IG Fiberglass, Hayward S-244T High Rate Sand filter, Hayward 1 HP pump

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

    Re: Is TA of 200 too high when PH is stable?

    With a cover, PH can be quite stable despite high TA. However, rare/unlikely events like a rain storm with the cover open could raise PH quite rapidly which could be a real issue given your iron level. In the short run you are fine, but the situation is a little usable, not normally a problem but poised to become a problem quickly.

    The same thing can be said about CYA below 10. With the cover on that isn't an issue, but it doesn't take all that long with the cover off to use up all of your chlorine. We recommend having CYA around 20 to 30 so that the chlorine can survive several hours with the cover off and people swimming. CYA around 20 also cuts down on the possibility of CC accumulating (which can be an issue with covers that are on almost all the time).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Re: Is TA of 200 too high when PH is stable?

    Yep, found out that you're correct about the CL disappearing quickly without any CYA when the cover is open. Give it a couple of hours, and it's essentially all gone on a sunny day. I'll work on raising the CYA up to at least 20 to provide greater stability.
    21,000 gallon, IG Fiberglass, Hayward S-244T High Rate Sand filter, Hayward 1 HP pump

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