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Thread: Borates and TA

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    rabbet's Avatar
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    Borates and TA

    Is it essential to bring the TA to the correct range when adding borates?
    My TA never gets below 120.
    Today's readings:
    FC 4.5
    CC .5
    PH 7.7
    TA 130
    CYA 30
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

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    Re: Borates and TA

    The thing is, with borates in the pool you are going to have a much harder time moving the TA. You can lower TA by bringing pH down to 7.2, then let it rise back to 7.7, etc.

    Why are you adding borates? For pH control?
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Re: Borates and TA

    rabbet, I tried and tried to get my TA down to recommended levels before adding borates and finally gave up. I went ahead and did the borates and just live with rising pH (which was happening before anyway). I'm happy with the results. I have since switched my fill water source and hope to get TA under control next season after a partial drain and refill in the spring.
    18'x4' AG Intex Ultra Frame, 6,700 gal., assembled new 2013; Mods: Hayward EC50C90 Perflex filter & 1 h.p. PowerFlo Matrix pump, Fiber Clear cellulose D.E. substitute, Hayward H100ID1 100,000 BTU NG heater, a pair of 2'x20' Sungrabber solar heaters via the original Intex 635T pump, grey Hydro Tools through-the-wall skimmer, Confer steps/ladder system & Cover Free chemical pool cover. The Summer of Mods!

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    rabbet's Avatar
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    Re: Borates and TA

    I hoped for reduced chlorine usage and pH would be more stable and it might help with algae.
    40K gallon IG painted concrete
    no skimmers
    Triton II sand filter
    2 HP Hayward pump
    Built June 1950

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    Re: Borates and TA

    Quote Originally Posted by rabbet View Post
    I hoped for reduced chlorine usage and pH would be more stable and it might help with algae.
    My chlorine usage has been the same, if not slightly better, and algae control around my steps has been much better.
    18'x4' AG Intex Ultra Frame, 6,700 gal., assembled new 2013; Mods: Hayward EC50C90 Perflex filter & 1 h.p. PowerFlo Matrix pump, Fiber Clear cellulose D.E. substitute, Hayward H100ID1 100,000 BTU NG heater, a pair of 2'x20' Sungrabber solar heaters via the original Intex 635T pump, grey Hydro Tools through-the-wall skimmer, Confer steps/ladder system & Cover Free chemical pool cover. The Summer of Mods!

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    Re: Borates and TA

    Borates won't affect chlorine usage, and isn't an algae control. But, it can help a bit with algae should you fall below target level for a very short period of time.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Borates and TA

    If you want to do borate additions, use boric acid instead of borax. It is acidic going into the water and doesn't require MA like borax does to keep the pH down. The additional acidity of the boric acid could help lower the TA a bit but it probably won't be too measurable.

    Because of the high pKa of borates in pool water (pKa ~ 9.0), about 90-95% of the boron will exist as boric acid at normal pool pH. Better to start that way from the beginning

    Do note that boric acid is more expensive than borax/MA but way easier to use (and you can use the left over BA as ant poison!!)

    Borates do not react with FC per se, but they do reduce chlorine consumption through the secondary effect of being a mild disinfectant. Both my acid-demand and FC were improved by borates. My SWG runs about 33% lower (from 45% power setting to 30% setting) and acid additions from once every other day to once every 5 days.

    Borates also improved the look and feel of my water. My wife likes the pool water a lot better and she says showering off the pool water is a lot easier. Borates do act as a mild softening agent (binds with Mg and Ca) so washing off is easier.






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    Re: Borates and TA

    Quote Originally Posted by SunnyOptimism View Post
    If you want to do borate additions, use boric acid instead of borax. It is acidic going into the water and doesn't require MA like borax does to keep the pH down. The additional acidity of the boric acid could help lower the TA a bit but it probably won't be too measurable.
    :
    Borates also improved the look and feel of my water. My wife likes the pool water a lot better and she says showering off the pool water is a lot easier. Borates do act as a mild softening agent (binds with Mg and Ca) so washing off is easier.
    Though boric acid is mildly acidic, it also contributes to TA because it is a weak acid. So the addition of 50 ppm borates (ppm Boron) from boric acid does not change the TA because the drop in pH lowers the TA by the same amount that it rises from the borate ion (there is a very minor drop of 0.1 ppm due to an increase in ionic strength).

    ........................... +TA ..... -TA
    B(OH)3 + H2O ---> B(OH)4- + H+
    Boric Acid + Water ---> Borate Ion + Hydrogen Ion

    Starting with a pH of 7.5 and a normal initial TA level, the pH drops to 7.3 and the carbonate alkalinity drops by 2.5 ppm. So for practical purposes, one can ignore the TA effect from the borates, at least near a pH of 7.5.

    Though the borates do form ion pairs with magnesium and calcium, this effect at pool borate concentrations and pH is negligible (only 0.1% of total calcium is bound to borate, but the change in ionic strength effectively keeps calcium ion concentration about the same). When 20 Mule Team Borax is used in the wash, the instructions are to use 1/2 cup or 1 tablespoon per gallon which would be 443 ppm, but it would also raise the pH to close to 9.1 where the borate ion concentration is much higher so at 300 ppm CH would sequester around 15% of total calcium.

    Any effects on showering may be related to changes in surface tension so that the water feels like it's silkier since it may not bead up as much.
    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: Borates and TA

    @chemgeek,

    The reference paper I read did not indicate that there was a measureable surface tension difference with or without borates. Have you come upon any newer information?

    Reference - http://members.iinet.net.au/~jorobbirch/Boric_acid.pdf



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    Re: Borates and TA

    I just wrote this post that refers to a recent experiment done to measure the surface tension difference. It's a pool owner's measurement and not a peer-reviewed published paper, but it's better than nothing.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Borates and TA

    I saw that show up in my Tapatalk time line. Thank you!

    And thank you for all of your expertise and clarifying posts. I greatly appreciate the rigorous scientific analyses you bring to the discussion threads.

    As for surface tension, I believe using an optical microscope that directly measures the contact angles of a water droplet on a glass surface is the definitive measure of surface tension. We used dry oxidized silicon wafers and H-terminated silicon (HF stripped Si) to measure droplet sizes and contact angles. In our plating baths, we did crude surface tension testing using a loop of wire in which you would time how long a film of the solution would persist before breaking (like a magic bubble wand). The former being objective and definitive while the later was a great spot test. I'll have to think about the scale pull force test....




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