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Thread: Boric acid and pH/TA

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    Boric acid and pH/TA

    I just read this thread and had a question about the use of boric acid vs. borax.

    I understand the need to add muriatic acid when using Borax in order to counteract the pH rise.

    My question is on the other side of the equation. If you use boric acid to add borates, should you anticipate seeing a drop in pH and TA since you're using an acid?

    I'm asking primarily because I am considering the borates route for my new pool. My fill water is particularly high in TA. My initial test had me at 210 ppm. I have gotten it to about 130 using the MA and aeration method. But once I get my TA below 100 ppm, I am considering using boric acid instead of borax for borate addition so as not to undo all the work I've been doing to adjust my TA with the muriatic acid.

    If there is a pH/TA drop associated with boric acid, is it significant enough that it's best to stop my efforts to reduce TA with muriatic where I am now, adjust the borate level with boric acid, then finish my TA reduction once I see where I am after the boric acid treatment?

    Or should I just stay the course on my TA, get it where I want it, then go after borates?
    12,500 gallon, in-ground Grecian Rectangle (vinyl liner). Installed June 2014. Sand filter, SWG for chlorination. TF-100 test kit.
    Located in Edmond, OK

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    JasonLion's Avatar
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    Re: Boric acid and pH/TA

    Boric acid is a weak acid, PH will go down a little, but not usually by enough to matter. TA will go down a tiny bit due to the acidity and up a medium amount due to adding borates, for a net small increase.

    You choice of chemical to use to add borates doesn't have any impact on your TA. TA will go up by the same small amount when adding borates regardless of which route you go.

    It is easier to lower TA first, but it is possible to lower TA after adding borates. Note that if you have high TA fill water, keeping TA low may not be practical regardless.
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    poolnoob.ca's Avatar
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    Re: Boric acid and pH/TA

    using the default settings of pool math for a 10K gallon pool, adding 400 oz. of boric acid to raise the borates to 52ppm gives a pH decrease of 0.3
    32,000L Fibreglass Leisure Pools IG 12.5'x23'x5' Pump: AstralPools BX1 1.0HP
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    Re: Boric acid and pH/TA

    Quote Originally Posted by JasonLion View Post
    Boric acid is a weak acid, PH will go down a little, but not usually by enough to matter. TA will go down a tiny bit due to the acidity and up a medium amount due to adding borates, for a net small increase.

    You choice of chemical to use to add borates doesn't have any impact on your TA. TA will go up by the same small amount when adding borates regardless of which route you go.

    It is easier to lower TA first, but it is possible to lower TA after adding borates. Note that if you have high TA fill water, keeping TA low may not be practical regardless.
    So it sounds like staying the course is my best option. I have been seeing progress (albiet slower than my impatient nature would like) with my efforts to reduce TA using the acid and aerate method. I can continue to lower my TA and get it to my desired range, then go with boric acid.

    With high TA fill water and an SWG, I have come to grips with the fact that I will likely always need to have some MA on hand to keep my pH in check, and to knock down the TA if I have to replace a significant amount of water.
    12,500 gallon, in-ground Grecian Rectangle (vinyl liner). Installed June 2014. Sand filter, SWG for chlorination. TF-100 test kit.
    Located in Edmond, OK

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    bobodaclown's Avatar
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    Re: Boric acid and pH/TA

    I did the borax the first time, then went the boric acid route. Got mine from Duda Diesel, order from eBay. No complaints.
    http://www.troublefreepool.com/threa...ght=boric+acid
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Re: Boric acid and pH/TA

    I've found after adding boric acid my PH has slowed down a lot on it's rising. I still have to add MA but not nearly as much as before the BA addition. Right now I'm adding MA on a weekly basis compared to almost every other day before the BA addition. I will note though that my TA number was at 70 before I added the boric acid.
    IG Pebbletec Blue Tahoe; Paddock Pool PCC 2000 pop-up; 22,275 gal 32' x 16' Diving with Auto-Fill
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    1 1/2 Whisperflo dedicated to Rock Waterfall; TF-100; Taylor K-1766; Pool Built in 1997

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