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Thread: pH drifting up

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    pH drifting up

    This year, I made the switch from tri/dichlor to liquid chlorine, in both my pool and spa, and have been rewarded with constant CYA levels, which is very pleasing. However, I have been having to deal with a new problem, especially in my spa: pH drifting upward. I have a 355 gal spa, and every time I use the jets, the aeration causes my pH to go up by at least 0.5. Every time I test it, it's up in the 7.9 - 8.0 range or higher. I put in acid to lower it back down to 7.3 or 7.4, but another use with the jets and it's too high again. I try to keep TA around 130 - 150, which is supposed to buffer against the pH swings, but it doesn't seem to be doing much good. And then, every time I lower pH with acid, I'm also lowering TA, and so I have to add baking soda to counteract that. Before, all I had to use was dichlor, which also lowered pH, counteracting the aeration somewhat, and only occasionally had to add acid -- and hardly ever added baking soda. (CH and CYA in my spa are 130 and 35, respectively, FYI.) Things were more convenient before.

    Similarly, in the pool, though not as bad. Since the switch, which coincided with a drain and refill, I've been having to add about 3-4 gal of muriatic acid (14.5%) a month, with the requisite baking soda to keep TA constant. (I've been keeping CYA in the pool around 65 -- we have very sunny summers.)

    Does this sound normal? Is it the price to pay to keep CYA constant?
    Todd Wilson, Fresno, CA (July: 82o avg, 110o max; Dec: 45o avg, 15o min)
    Pool: IG, pebbled, 21K gal, 520 ft2 4-cartridge filter, 1.5 hp pump, Paramount PV3 in-floor cleaning system
    Spa: Stand-alone, 355 gal, 100o - 102o, no ozonator

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    Mod Squad JohnT's Avatar
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    Re: pH drifting up

    You need to let your TA come down. The TA causes your pH to rise. A level more around 90ppm would probably be better, maybe even lower.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
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    stev32k's Avatar
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    Re: pH drifting up

    If you are using Wal-Mart or some other off-brand of bleach try switching to chlorox. I had the same problem when using the Wal-Mart brand and when I switched the pH quit rising. Sometimes a batch of bleach will contain an excess of caustic that will cause the pH to increase.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
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    JasonLion's Avatar
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    Re: pH drifting up

    I doubt it has much to do with the brand of bleach. With TA over 130, PH is sure to rise in the spa exactly as described. Lowering TA is definitely the first thing to try.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: pH drifting up

    OK, I'll bring the TA in the spa down to the 60 - 80 range and see if that fixes the problem, thanks. How about the second part of my question, in relation to the pool: "Since the switch [to liquid chlorine], which coincided with a drain and refill, I've been having to add about 3-4 gal of muriatic acid (14.5%) a month, with the requisite baking soda to keep TA constant.... Does this sound normal? Is it the price to pay to keep CYA constant?" I've kept TA in the pool around 80. The pool doesn't have any water features, although the PV3 system sometimes creates some bubbling on the surface from those nozzles that are on steps near the wall.
    Todd Wilson, Fresno, CA (July: 82o avg, 110o max; Dec: 45o avg, 15o min)
    Pool: IG, pebbled, 21K gal, 520 ft2 4-cartridge filter, 1.5 hp pump, Paramount PV3 in-floor cleaning system
    Spa: Stand-alone, 355 gal, 100o - 102o, no ozonator

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    Richard320's Avatar
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    Re: pH drifting up

    Quote Originally Posted by twilson
    OK, I'll bring the TA in the spa down to the 60 - 80 range and see if that fixes the problem, thanks. How about the second part of my question, in relation to the pool: "Since the switch [to liquid chlorine], which coincided with a drain and refill, I've been having to add about 3-4 gal of muriatic acid (14.5%) a month, with the requisite baking soda to keep TA constant.... Does this sound normal? Is it the price to pay to keep CYA constant?" I've kept TA in the pool around 80. The pool doesn't have any water features, although the PV3 system sometimes creates some bubbling on the surface from those nozzles that are on steps near the wall.
    Why mix base and acid? They just cancel each other. My pool has a spa that overflows into the pool, so pH is constantly rising. I use a lot of acid. But I've finally got TA down to 80, and it seems to hold there longer. Hasn't changed in 4 days now. If i were you, I'd add acid as needed to keep pH in check and not worry about TA unless it got down to below 70.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Re: pH drifting up

    My tub runs at TA 50. I also use borates and noticed a huge improvement in pH control. We only use it once or twice a week but my records show I've added acid only once in the past month.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
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