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Thread: High TA, High CA

  1. Back To Top    #1

    Join Date
    Jun 2014

    High TA, High CA

    I have always loved chemistry so the issue of pool chemistry is actually fun for me; but I will have to relearn stuff from many years ago. I just "inherited" a pool in the house we purchased where the original owner scoffed at the finding of very high cyanuric acid levels (> 300 with 50:50 dilution and only after 1:4 dilution were levels 99. The prior owner's test kit only checked pH and chlorine--that's it. My initial testing also disclosed pH 8.4, sky high TA, high calcium hardness, but total chlorine (TC) and free chlorine (FC) levels at 3 ppm. My pool water is crystal clear.

    I have gone through two pool "service" people and dismissed the first because he was ripping me off by overcharging me on replacement parts e.g., a float that retails for $24 and a charge of over $100. Everyone is entitled to a profit but no one should be financially raping another. The 2nd guy I just dismissed because his every two week service was so superficial that when I checked the skimmer and the pool filter after he left both had not been cleaned. Moreover, he said nothing about the very high TA, CH (calcium hardness), but did state that I had to empty (totally) the pool.

    My questions/comments to the forum:

    I have been told that it is NOT a good idea to totally empty your pool unless you know what depth your ground water is. If the ground water is high the complete emptying of your pool might result in your pool actually being lifted out of the ground. T or F? At any rate, my plans are to empty the pool by 25-50%.

    To replace 10,000 gallons of water with a local water service will cost me $400 (I am on a well producing 2 gallons per minute). We are having extremely hot weather and the well is quite old. I am tempted to replace the pool water gradually via the Pentair sand filter (waste water), and use the well water. The well water chemistry reveals a low CH, pH of 7.3, no cyanuric acid, but a TA of 170.

    Questions: Using the Pool Math calculator on this website, I am able to see the amount of muriatic acid to add to lower TA and lower pH, and then aerate to bring pH up to a slightly higher level.
    I have also been told that cyanuric acid is heavier than the rest of the pool water and will be in higher concentration at the bottom of the pool near the main drain, which is what I will be using on the waste water setting of the Pentair sand filter. Does it make sense for me to proceed by emptying 25-50% of the water, replacing it with well water, checking the chemistry, recalculating all the chemical levels and adding acid, aerating and hopefully seeing a significant trend for the better?

    Is this true about cyanuric acid being somewhat more selectively drained when emptying the pool from the main drain?

    If I purchase water from outside, the benefit would be that there would be no significant levels of alkalinity. But is this of any advantage given that adding muriatic acid is not expensive and quite simple?

    Will my chances of achieving good pool chemistry be far better by emptying half the pool and replacing it with purchased water, or do I have a good chance of being successful by emptying 25% of the pool water and replacing it with my well water?

    Am I safe to swim in the pool given the cyanuric acid levels, despite the chlorine levels being good and the pool water clear? My understanding is that the high CA levels do not allow for sufficient fungal and bacterial killing and that anyone swimming in a pool with such levels is at a risk for major infection. Is this true?

    Stephen B. Strum
    Jacksonville, Oregon
    16,100 gallons, in-ground, chlorinated pool using well water (low producing well), sand filter Pentair Meteor, Polaris 380 pool cleaner with booster pump, Propane and passive Solar heaters.

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: High TA, High CA

    Yes, pools can float right out of the ground.

    The CYA settles to the bottom (sometimes top) stuff is nonsense. Once CYA is dissolved and mixed in it is spread uniformly through the water.

    If the only issue is TA, I would use local (inexpensive) water.

    You need to get CYA down to roughly 60, however much water replacement that requires.

    If you follow our guidelines for FC level, and actually know your CYA level (essentially impossible if CYA is over 200) and the water is clear then swimming is fine. CYA lowers the effectiveness of chlorine, but by raising the FC level you bring chlorine back to the same activity level it would have had.
    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

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