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Thread: Low PH -- High Alkalinity

  1. #1
    Join Date
    Jul 2006

    Default Low PH -- High Alkalinity

    I wish I had found this forum and read every word of it earlier. We have 52" 24' round pool, which I believe has a volume of 13,600 gallons. I'm about to close our pool for the first time so I want to be extra careful that it's balanced. I don't want a mess on my hands in spring.

    I took it in to a local pool place that provides more accurate water testing than many of the home tests. I found that my pH and alkalinity were high (7.9 and 216) despite the fact that my stupid test strips had been showing the pH at about 7.2. I added about 1.5 quarts of muriatic acid and went back to the same place a few days later for another test. I probably should have added more, but I wanted to see the effect first.

    I found that my pH was still 7.8 and my total alkalinity was still 176. The guy at the pool store told me to add 1 gallon of muriatic acid. I thought that sounded like too much, especially at one time. I asked him 'you're sure one gallon and your sure all at one time'. He confirmed that it would not be a problem.

    I added the gallon of muriatic acid two days ago. I did try to spread it out since I figured I probably shouldn't be adding so much at one time. I just borrowed a neighbor's 'drop' test kit and tested the water. It tells me the pH is 7.2+ and the total alkalinity is about 160-170 ppm. (Seemed to be 16 or 17 drops when it changed from purple to clear.)

    I am going to take one more water sample back to the pool store to verify my results, but my question are...

    1. Are these results in an acceptable range to consider the pool water balanced and ready for closing or do I need to bring the alkanity down and the pH up?

    2. If not, how do I bring my akalinity down to closer to 100 ppm without lowering my pH?

    Thank you.


  2. #2
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Nov 2004

    Default Re: Low PH -- High Alkalinity

    Welcome to the forum!

    Assuming that your CYA wasn't really extreme (I assumed 40 ppm) then 1.5 quarts (6 cups) of Muriatic Acid (31.45%) in your 13,600 gallon pool with a pH of 7.9 and a TA of 216 should have resulted in a pH of 7.4 and a TA of 203. So the numbers that your pool store then gave you of 7.8 and 176 do not make sense.

    Furthermore, if you were to start at 7.8 and 176 and then add 1 gallons of acid, you would end up with a pH of 6.9 and a TA of 141. So that is too much to add.

    I would be very suspect of the numbers you are getting from the pool store. Get an accurate test kit such as the Taylor K-2006 or Ben's kit and test the pool water yourself.

    As for lowering the TA, follow Ben's Lowering Your Alkalinity procedure which is the only truly effective way to lower the TA. The advice from pool stores to simply add acid without first lowering the TA and aerating is just plain wrong and ineffective.

    My guess is that your pH is already on the low side, but that due to carbon dioxide outgassing (due to the high TA and low pH combination) the pH will rise (and the TA will stay the same). So again, get a decent test kit and test the water yourself and then follow Ben's procedure to get your TA down.

    Keep us posted with how it goes.


  3. #3
    CarlD's Avatar
    CarlD is offline Super Moderator Quark Inspector CarlD 4 stars CarlD 4 stars CarlD 4 stars CarlD 4 stars CarlD 4 stars CarlD 4 stars
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    Dec 1969
    North Central NJ

    Default Re: Low PH -- High Alkalinity

    Much ado about nothing!

    As usual, the pool store cretin has NO idea what he's talking about.

    1) Muriatic acid is fine but you do have to be careful adding it. I like to dilute it in a 5 gallon bucket first, and never use more than 1 quart at a time.

    2) You have a vinyl pool If the acid collects on the liner it starts to melt it. Bad, very bad.

    3) Normal T/A range is supposed to be 80-125ppm. HOWEVER: with a vinyl pool you can safely allow it to go to 180 without ANY problems.

    4) For swimming, pH of 7.2 is still safe for swimming and T/A of 170 is fine.

    5) For closing, I like to see higher pH--around 7.6. Lots of places have acid rain (like NJ where I live). But if you raise pH, TA will go up to...UNLESS...

    6) You go find the method for lowering T/A here:
    a.Lower you pH to 7.0 to 7.2, no higher, no lower.
    b.Aerate your water. You can just leave it uncovered with the pump on, or speed it up with a gang of 12 year olds, a fountain, or a screw in sprayer (this replaces your eyeball in your return and is about 20 bucks.
    c. pH should rise without T/A rising.
    d. Add acid again to drop pH to 7.0-7.2
    e. Aerate again.
    f. When T/A is where you want it (say, 125 for your pool), aerate to raise pH, then add Borax (NOT Soda Ash!) to raise it further. T/A will go up a little with the Borax, but that's OK. The Soda Ash, instead, will undo all your good work.

    Or you can just use Borax to raise your pH. T/A will rise with it, but if it's below 180, don't worry, just close. If it's below 200, you can either lower T/A or just go ahead and close. Over 200, it's easy to get white cloudy water, so I like 180 as the safety margin below that.

    Still, if the water goes WHITE and cloudy from too high TA over the winter it's not a tough fix--it's not algae growing--and just adding acid in the spring should clear it.

    Just my take.

    16'x40' rectangle 19K gal AG vinyl pool; ; Hayward T210 sand filter and 2 Speed Superpump 1hp pump; Solar heated. Test kit: PS 233; PF:6.3; Autopilot SWCG

  4. #4
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Nov 2004

    Default Re: Low PH -- High Alkalinity

    Thanks Carl. I missed the part about this being a vinyl pool. As you said, the TA level is no problem in this case except possibly causing a greater tendency for upward pH drift (or greater use of acid to keep pH lower).


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