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Thread: Lowering Alkalinity

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    Lowering Alkalinity

    I was reading the apply acid / aerate procedures for lowering TA and ended up scratching my head a bit .. if Borax raises pH without affecting alkalinity, why is aeration necessary? I ask because I don't have an effective aeration method at the moment but do have somewhat elevated TA and CH (both around 230) which I suspect may be contributing to my cloudy water issues. Why not just pair up Muriatic Acid and Borax to fix the TA issue in a more timely fashion?

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    The short answer is that it won't work!

    EDIT by TMQ - to remove bad information so no one can say I pool-stored them!

    Aerating the pool can be accomplished in different ways, including several kids splashing for an afternoon, or even aiming your returns up to the surface.

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    Re: Lowering Alkalinity

    Muriatic will reverse the effect of Borax and vice versa. You pH will bob up and down as you apply one or the other but your TA will, essentially, be unaffected. You can only permanently lower Alk by bubbling it off.

    (Evan and Richard are gonna' kill me for my redneck terminology )

    PS - I would consider your CH perfectly normal but your Alk is quite high.
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    Ah. Well that.s interesting, I didn't realize that's how it worked. It seems odd that stores sell acids as "Alkaline lowering" when it's apparently just an enabler. Even the book that comes with the Taylor kits implies acid reduces TA ..

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    Quote Originally Posted by lebaige
    It seems odd that stores sell acids as "Alkaline lowering" when it's apparently just an enabler. Even the book that comes with the Taylor kits implies acid reduces TA ..
    Actually, it sorta' does. I envision TA as traveling with the pH...up or down...which it does. The only way you can move them opposite of each other is aerating. Not very scientific but it keeps it so I can understand it.

    Don't be surprised by the misleading info on pool store chemistry. 95% of the folks who come to the forum think shock is a product you buy. Who can blame them if they've ever visited a pool store?
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    Acid lowers PH AND TA. Aeration raises PH but not TA. So here is how it works.

    Add acid - lower TA & PH
    Aerate - Raise PH via outgassing
    Repeat until TA is down where you need it

    As you can see PH will go down then back up but TA will keep going down.

    Borax does not raise TA as much as PH but it does raise TA a little so theoretically, you could use Borax in the process but it would take a lot of Borax and $$ to make a significant shift.

    [Edit]
    Also, you could theoretically add enough acid to get TA where you want it but then PH could be way too low causing damage to the pool and/or equipment. This is why it is done in steps.

    I once did an experiment where I raised the PH in my spa, 700 gallons, .4 units with 30 minutes of jet bubbles on. So it is pretty effective method.
    Mark
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  7. Back To Top    #7
    See, the above is what I thought happened. I was under the impression that the ACID is what reduced alkalinity and pH, and the aeration was simply an economical method to raise the pH back up without affecting the TA level you just lowered. Since borax is also supposed to raise pH without affecting TA, I was pondering using it in lieu of aeration.

    Out of curiosity, is there a guide somewhere for the actual use of Borax, i.e. how much to achieve what pH jump?

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    Guest
    Here is the long answer. Total alkalinity is comprised of three things, carbonates, bicarbonates,and carbonic acid in the water. The measurable part of TA is the carbonates and bicarbonates. When you lower th pH you lower the amount of measurable carbonates and bicarbonates because they convert to carbonic acid (carbon dioxide dissolved in water, think seltzer--which is essentially just carbonic acid!) Now if you just raise the pH back up the carbonic acid will convert back to carbonates and bicarbonates and your TA will rise again!
    BUT (this is the cool part!) if you lower the pH, thus lowering the measurable TA and get rid of the excess carbon dioxide in the water by aerating your pH will rise but your TA won't becuase you are just reducing the amount of carbonic acid without converting it back into meaurable carbonates and bicarbonates! (think shaking up a bottle of seltzer to make it go flat!)
    Pretty cool, isn't it!

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    Thanks for explaining it in simpler terms Waterbear. It makes even more sense now.
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    Just wanted to correct what Mark said about Borax (he's corrected me a few times about pump equations so I'm just returning the favor ). Borax will raise the TA slightly more than acid lowers it. That is, for the same pH move (in opposite directions) Muriatic Acid or Dry Acid (sodium bisulfate) will lower the TA and Borax will raise it exactly the same amount plus a small amount more. The small amount more is due to the borates (boric acid) from Borax actually being a pH buffer itself -- one that has a very small contribution to TA (but is a great pH buffer for preventing a rise in pH -- TA only measures the pH buffering preventing a drop in pH, not a rise).

    What is true is that Borax does not add carbonates to the pool the way that "pH Up" products, which are sodium carbonate, do. Sodium Carbonate is literally like adding baking soda or "Alkalinity Up" which is sodium bicarbonate (aka sodium hydrogen carbonate) plus an additional pure base (such as lye -- see below). So Borax will not add to that part of TA that leads to carbon dioxide outgassing and the tendency for pH to rise.

    So you might ask, is there a base that raises pH and has the TA rise by EXACTLY the same amount as acid lowered it? That is, is there a base that is a true opposite to an acid? The answer is yes. It is called lye / caustic soda / sodium hydroxide. For whatever reason, it is not readily available except for those who make soap. I'm not sure why it's not made available at pool stores. It's no more toxic or dangerous than Muriatic Acid -- both need to be handled carefully.

    Richard
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    See, this is why I never try to answer the tricky questions... I usually have the gist of it, but get the facts all screwed up!

    Thanks guys for not coming down on me too hard for that! I'll try to stick to baqua conversions from now on, since I seem to have that down...

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
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  12. Back To Top    #12
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    Quote Originally Posted by chem geek
    se.

    So you might ask, is there a base that raises pH and has the TA rise by EXACTLY the same amount as acid lowered it? That is, is there a base that is a true opposite to an acid? The answer is yes. It is called lye / caustic soda / sodium hydroxide. For whatever reason, it is not readily available except for those who make soap. I'm not sure why it's not made available at pool stores. It's no more toxic or dangerous than Muriatic Acid -- both need to be handled carefully.

    Richard
    Most grocery and hardware stores sell lye! It's usually the Red Devil brand and it's in the drain cleaner aisle. I used to make my own soap and bought it all the time!

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    Lebaige,

    See? You had to ask, didn't you?

    I'm gonna' consume a few adult beverages and try to understand the bottom half of this thread. On second thought, I may just poke a sharp stick in my eye!

    I am truly jealous of you folks who have such a good grasp on this stuff and I'm glad ya'll are willing to share it on this forum. I actually believe small portions of your knowledge penetrate my thick skull from time to time....but then they get stuck and I can't retrieve them.
    Dave S. - Forum owner
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    Quote Originally Posted by duraleigh
    Lebaige,

    See? You had to ask, didn't you?

    I'm gonna' consume a few adult beverages and try to understand the bottom half of this thread. On second thought, I may just poke a sharp stick in my eye!

    I am truly jealous of you folks who have such a good grasp on this stuff and I'm glad ya'll are willing to share it on this forum. I actually believe small portions of your knowledge penetrate my thick skull from time to time....but then they get stuck and I can't retrieve them.
    Dave,
    Yours is a condition that afflicts many of us (the overconsumption of certain beverages, the thick skull, the bony tissue overhanging the eyes, the inability to comprehend Evan and Richard, etc.).

    By the way, what's with the constant reference in your sig to the 900 lbs. sand filter? Are you compensating for something or what?

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    Quote Originally Posted by KurtV
    By the way, what's with the constant reference in your sig to the 900 lbs. sand filter? Are you compensating for something or what?
    Ka-zing!! Ouch and double ouch!!

    I'm slinking off the computer as we speak!!
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  16. Back To Top    #16

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    So just to be perfectly clear -- ONLY AERATION can be used as part of a procedure to lowering TA. There is NO BASE that should be used to raise pH when one wants to lower TA. You will simply swing back and forth in TA if you do that. You could accidentally lower the TA a little while the pH was low, but it would be due to aeration of some sort. The following is the TA lowering procedure I've posted elsewhere (and is based on Ben's original procedure here).

    ACTIVITY .......... pH .... TA ... (The following assumes 6.8 is the lowest measurement on the pH test kit)
    ==================

    Acid ..................... - ........ - ... Add enough acid to bring pH down to 7.0

    Aeration ............. + ....... 0 ... Aerate until pH rises to 7.2
    Acid ..................... - ........ - ... Add enough acid to bring pH down from 7.2 to 7.0 (you may continue to aerate while you do this)
    ------------------------------------
    Aeration & Acid .. 0 ....... - ... Continue this combination (cycling of the two above) until TA is at the target you want

    then AFTER you have reached your target TA,

    Aeration ............. + ....... 0 ... Aerate until the pH rises to your target pH (say, 7.5).

    ==================
    Net of Above ....... 0 ........ -

    As for how much Borax it takes to raise or lower pH, the answer unfortunately depends on the TA level (and CYA level) and the starting and ending pH levels. The following are a few examples of what one pound of 20 Mule Team Borax will do in 10,000 gallons of water with a CYA level of 30 ppm:

    at TA 80, will move pH from 7.00 to 7.11
    at TA 80, will move pH from 7.20 to 7.36
    at TA 80, will move pH from 7.40 to 7.63
    at TA 80, will move pH from 7.60 to 7.89
    at TA 80, will move pH from 7.80 to 8.11

    at TA 120, will move pH from 7.00 to 7.07
    at TA 120, will move pH from 7.20 to 7.31
    at TA 120, will move pH from 7.40 to 7.55
    at TA 120, will move pH from 7.60 to 7.80
    at TA 120, will move pH from 7.80 to 8.03

    So you can see that the same amount of Borax at higher TA makes the pH move less and that the same amount of Borax at higher pH makes the pH move more. Hope that helps.

    Richard
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    No matter how far I (and duraleigh) drag these threads into the dirt, there comes chem geek to restore order.

  18. Back To Top    #18
    Well I'm not a chemist but I understand that explanation, thanks!

    Of course, that begs the question .. if lye can be used as as a base with no unnecessarily added alkalinity, why do we use Borax? I'm almost positive I've seen it on sale in various hardware and grocery stores before ..

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    Guest
    Did a little checking and it seems that Reckett Benckiser has pulled Red Devil lye. Rumor is that it was used in meth labs.

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    Quote Originally Posted by chem geek
    Just wanted to correct what Mark said about Borax (he's corrected me a few times about pump equations so I'm just returning the favor ). Borax will raise the TA slightly more than acid lowers it. That is, for the same pH move (in opposite directions) Muriatic Acid or Dry Acid (sodium bisulfate) will lower the TA and Borax will raise it exactly the same amount plus a small amount more. The small amount more is due to the borates (boric acid) from Borax actually being a pH buffer itself -- one that has a very small contribution to TA (but is a great pH buffer for preventing a rise in pH -- TA only measures the pH buffering preventing a drop in pH, not a rise).

    After adding Borates to the pool, I noticed a slight drop in my TA which is where the comment came from but now I realize that it was probably due to the over dosing of acid since the PH was lower than when I started. I need to be more careful about assumptions. You know what they say happens when you *** u me.

    Richard
    So do I need to plant a tree after lowering my TA to offset the carbon loading?
    Mark
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