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Thread: pH out of control

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    pH out of control

    Hi all,

    I'm a new owner of a 19K gal gunite pool in SoCal.

    I've been battling high pH (7.8-8.0) for awhile now, with a normal? TA ranging from 100-120. I've been adding about a quart of muriatic acid every 3-4 days, but I've NEVER had the pH go into the 7.4 range.

    When I first bought the house, I had a pool guy come over to teach me the basics. He took tests and told me my CYA was off the charts (the previous owner just had a floater with chlorine tabs). After paying for a drain/acid wash/DE filter clean/re-fill, he explained the side-effect to too much conditioner (caused be the tabs), and recommended I use liquid.

    The pool has been sparkling and beautiful since, but with two nagging issues. First, I haven't been able to get pH down and secondly my FC hasn't been completely stable because I'm still not sure how much to add daily (1,2,3 quarts?). It has been as low as .4 (barely registering) to 2.5. I use Home Depot's Kem-Tek which has 10% sodium hypochlorite.

    I just found out that the Kem-Tek I use has a pH of 12!! With that in mind, it sounds like I'm solving one problem (low FC) and creating another (high pH). My latest TA measurement (today) is the highest ever, at 190. I immediately put in a quart of muriatic acid.

    I've been doing a ton of research here, but I'm still not sure if I'm talking intelligently. Any advice would be appreciated!
    20K Gallon Gunite Inground Pool/Spa, DE Filter with 1.5HP WhisperFlo Pump

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    Mod Squad JohnT's Avatar
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    Re: pH out of control

    Adding liquid chlorine is pH neutral overall. A quart af acid every 3-4 days isn't a lot. You should add more acid to push the pH down into the low 7 range. If you keep it there, your TA will drop over time, or you can accelerate the process by aerating the water. You'll need to add acid much more often if you aerate.
    TFP Moderator
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    Re: pH out of control

    Quote Originally Posted by JohnT
    Adding liquid chlorine is pH neutral overall.
    Are you sure about that? The MSDS for the Kem-Tek I buy clearly states 12: http://www.homedepot.com/catalog/pdfIma ... dd3bb3.pdf

    My pool gets lots of direct sunlight, and a ton of aeration (the pool return comes from the spa which waterfalls into the pool).

    So is the recommendation to add a quart a day until pH (and then eventually) TA come down? I heard it wasn't wise to use more than 32oz/day.
    20K Gallon Gunite Inground Pool/Spa, DE Filter with 1.5HP WhisperFlo Pump

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    Smykowski's Avatar
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    Re: pH out of control

    Quote Originally Posted by z0ner
    Are you sure about that? The MSDS for the Kem-Tek I buy clearly states 12: http://www.homedepot.com/catalog/pdfIma ... dd3bb3.pdf
    Yes. While the Kem-Tek itself is a strong base, the conversion to hypochlorous acid makes the chemical process pretty much pH neutral. Do a search, and you'll find plenty of evidence from ChemGeek on the forum.

    Quote Originally Posted by z0ner
    My pool gets lots of direct sunlight, and a ton of aeration (the pool return comes from the spa which waterfalls into the pool).
    The (slightly) high TA combined with the aeration is what's driving your pH up.

    Quote Originally Posted by z0ner
    So is the recommendation to add a quart a day until pH (and then eventually) TA come down? I heard it wasn't wise to use more than 32oz/day.
    How are you testing for pH? Strips or drops? If it's drops, trust your testing. If it's strips, dump them and get a good test kit.

    Assuming you're using drops, trust your testing and "it takes what it takes." I'd test every day, and do what it takes to keep your pH in the 7.2-7.4 range. The acid additions plus the aeration will bring the TA down eventually. (Remember that alkalinity is a pH buffer, so with high TA, it's going to take a lot of acid to move your pH.)
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: pH out of control

    Quote Originally Posted by Smykowski
    How are you testing for pH? Strips or drops? If it's drops, trust your testing. If it's strips, dump them and get a good test kit.
    I started out with a basic drops kit, and just recently became the proud owner of a TF-100. I still use the basic for everyday testing.

    Quote Originally Posted by Smykowski
    Assuming you're using drops, trust your testing and "it takes what it takes." I'd test every day, and do what it takes to keep your pH in the 7.2-7.4 range. The acid additions plus the aeration will bring the TA down eventually. (Remember that alkalinity is a pH buffer, so with high TA, it's going to take a lot of acid to move your pH.)
    Thank you both very much for your advice. I wanted to know if a) the liquid chlorine was responsible for the high pH, and b) (more importantly) to get the pH down. I'll update the thread with results as they come.
    20K Gallon Gunite Inground Pool/Spa, DE Filter with 1.5HP WhisperFlo Pump

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    Re: pH out of control

    The consumption/usage of chlorine is an acidic process that compensates for the rise in pH that occurs when you initially add the chlorine (see this post for technical details). The only net rise in pH from use of chlorinating liquid or bleach itself is from the "excess lye" in it. 10% chlorinating liquid with a pH of 12 is reasonable and has around 0.04% excess lye so not that much.

    The source of your pH rise is carbon dioxide outgassing from the pool due to your Total Alkalinity (TA) that is too high. You should lower it to at least 80 ppm if not 70 ppm. The large amount of aeration increases the rate of that outgassing, but a lower TA level will lessen that rate. Pools are intentionally over-carbonated to saturate the water with calcium carbonate to protect plaster surfaces and to provide some pH buffering, but TA is a SOURCE of rising pH itself. This is fine when using net acidic sources of chlorine such as Trichlor or Dichlor, but when using hypochlorite sources of chlorine one wants a lower TA level to lessen the pH rise from carbon dioxide outgassing.
    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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    Re: pH out of control

    Quote Originally Posted by z0ner
    Quote Originally Posted by Smykowski
    How are you testing for pH? Strips or drops? If it's drops, trust your testing. If it's strips, dump them and get a good test kit.
    I started out with a basic drops kit, and just recently became the proud owner of a TF-100. I still use the basic for everyday testing.

    Quote Originally Posted by Smykowski
    Assuming you're using drops, trust your testing and "it takes what it takes." I'd test every day, and do what it takes to keep your pH in the 7.2-7.4 range. The acid additions plus the aeration will bring the TA down eventually. (Remember that alkalinity is a pH buffer, so with high TA, it's going to take a lot of acid to move your pH.)
    Thank you both very much for your advice. I wanted to know if a) the liquid chlorine was responsible for the high pH, and b) (more importantly) to get the pH down. I'll update the thread with results as they come.
    I have been adding 32 oz of acid a day. I posted here to find out if it is normal in a new pool and people said no. I have a spa that waterfalls into the pool and there was an air leak into the spa jets causing lots of aeration. I sealed the leak (mostly) and turned down the spa returns and now I need about 32 oz every 4-5 days. My TA is around 60
    17,800 gallon, IG pool, 595 sq feet (17x35x4.5 avg rectangle), Hayward 525 cartridge filter, diamondbrite, 2 hp 2 speed hayward tristar filter, Stenner 45mhp10 automatically chlorinating

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    Re: pH out of control

    Well I started with a TA of 300 (well water) and that combined with my salt water generator I was adding around 32oz every other day and my pool is only ~6000 gallons. Now that I have my TA down under 100 and I added about 20ppm of borates I haven't added acid in almost a month and it is stable at 7.5.
    6500 gal, Intex 18'x48" above ground, 1hp Pro Sand Filter, TF100 Test Kit

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