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Thread: Heresy-Borates do not act as a buffer at pool pH levels

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    Heresy-Borates do not act as a buffer at pool pH levels

    I am helping a friend with a fiberglass pool and was looking for a better understanding of how little pools balance their chemicals. We ran tests and found our results did not agree with a pool store my friend had been using. I came across this site and decided to join. After reading a number of sticky's and posts, I realize I am writing heresy here, but I would like to clear up a few things on borates in the pool.

    When you dissolve borax in water, you get a weak lewis acid, boric acid and a base tetrahydroxy borate. The pH buffering ability of borax doesn't start until an upper pH of 8. The pKa of the boric acid is over 9 and this will be the area of highest buffering capacity. Borates and borax have virtually no buffering capacity in the pH range of 7-8 in a pool. Borates are weak alkaline products with weak alkaline chemistry. The silky feel is a type of saponification of oils from the body and not anything to do with a water characteristic. Saponification in its majestic form is mixing lye with animal fat to make soap. Hence the silky feel.

    The primary buffering capacity in pools is due to alkalinity. Specifically due to the bicarbonate buffering system. Once you go above pH 6.3 you have a carbonate-bicarbonate buffer until around a pH 8.3. This is why alkalinity is one of the most important chemical parameters to maintain in a pool. Alkalinity in our pools is mostly carbonate. The other half of the chemical species is not important and is just a counter ion. Carbon dioxide from the atmosphere and the carbonate part of alkalinity form a buffer system. This is a lesson one learns in Indiana since the ground water is typically 250-450ppm alkalinity. Proper maintenance of your alkalinity is the most important aspect of pool chemistry maintenance. You will fight an uphill battle until you get your alkalinity within acceptable ranges for your pool. You will waste time and money until you bring your alkalinity in line and keep it in line.
    Chemist and operator of community 220,000gal plaster pools.

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    I'm sure your post will bring some interesting discussion.

    This needs clarification....
    Proper maintenance of your alkalinity is the most important aspect of pool chemistry maintenance.
    My personal vote is for chlorine....I'm certainly not saying alkalinity isn't important, I just don't want newbies to dwell on adjusting their alkalinity while their pool turns into a green swamp.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    Well, I have no authority to discuss chemistry, so I will defer to those with more expertise on this subject. BUT, my experience with my one pool seems to confirm your assertion. I added borates with the hope that they would help to mitigate the ever rising PH in my pool, but so far I can tell no difference.

    That being said, I have no regrets with the addition because I like what the borates have done to the feel of the water, and I am trusting in their advertised algae-static properties.

    FWIW,
    Dave
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    wejones,

    What you wrote about the lack pH buffering for borates is absolutely, positively not true. Why do you believe that there is no pH buffering capability of the boric acid / borate ion buffering system at pH of 7-8 just because it's pKa is around 9.1? It is true that it's buffer capacity is lopsided where it has much more capacity at preventing higher pH than it does preventing lower pH, and it is also true that it's buffering effect is lower further away from a pH equal to its pKa, but it is NOT zero or too small to have an effect.

    Doing the precise calculations demonstrates the pH buffering effect from the borates and my own pool as well as others on this forum that use borates shows that it works in practice (i.e. in "real pools") as well. At the 50 ppm Borates level recommended on this forum when using borates, the pH buffering effect is demonstrated by the following examples starting with a pH of 7.5, TA of 80, CYA of 30 ppm.

    Add 3 cups of Muriatic Acid to 10,000 gallons (TA decreases by 9.4 ppm)
    with 0 ppm Borates: pH moves from 7.5 to 7.03
    with 50 ppm Borates: pH moves from 7.5 to 7.13 (some buffering effect, though not very strong)

    Add 1.5 cups of Soda Ash (washing soda) to 10,000 gallons (TA increases by 9.7 ppm)
    with 0 ppm Borates: pH moves from 7.5 to 7.98
    with 50 ppm Borates: pH moves from 7.69 (reasonable buffering effect; cuts pH rise by more than half in pH units)

    Add 3 cups of 20 Mule Team Borax to 10,000 gallons (TA increases by 4.9 ppm)
    with 0 ppm Borates: pH moves from 7.5 to 7.92
    with 50 ppm Borates: pH moves from 7.5 to 7.68 (and borates increases by 2.1 ppm)

    Outgassing of 0.37 pounds of carbon dioxide (TA does not change)
    with 0 ppm Borates: pH moves from 7.5 to 8.00
    with 50 ppm Borates: pH moves from 7.5 to 7.69

    You can calculate the above using my Pool Equations spreadsheet. If you find any problem with it, please let me know.

    As for the silky feel, what you wrote is certainly plausible and I really don't know if that's the cause or not. The water in my own pool with Borates doesn't seem to feel much different. I did notice that it tends to reduce surface tension somewhat since the meniscus in my water tests seems to be quite a bit flatter since the addition of the borates.

    The carbonate buffering system is also not at the ideal pH either, by the way. The pKa (accounting for ionic strength) for carbonic acid (including aqueous carbon dioxide) vs. bicarbonate ion is 6.3 while for bicarbonate ion vs. carbonate ion it is 10.2, neither of which is particularly close to 7.5 or 7-8. The carbonate buffer system is also not at its strongest buffering capacity though the 6.3 is close enough to 7 to have reasonably strong protection against the lowering of pH. The use of borates makes a nice complement since it mostly increases the buffering against a rise in pH and when using hypochlorite sources of chlorine it is a rise in pH that is what normally occurs (due to carbon dioxide outgassing). So one can lower the TA level to reduce the rate of pH rise from carbon dioxide outgassing and the use of Borates provides additional pH buffering right where you need it (i.e. against a rise in pH).

    It is certainly true that managing the TA is key to pH stability if one understands that a higher TA is not just providing more pH buffering, but is also a SOURCE of rising pH iteself and that this latter effect overwhelms the former at higher TA levels so that ironically a lower TA level has the pH be more stable when using pH net neutral sources of chlorine (i.e. hypochlorite sources) when accounting for the acidity of chlorine consumption/usage. On this forum we always first recommend getting the TA lower if there is a pH rise. The use of borates will not, by itself, reduce the amount of acid needed, but will only slow the rate of pH rise -- the amount of acid needed after the same amount of pH rise will be higher so the net over time is the same.

    Richard
    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: Heresy-Borates do not act as a buffer at pool pH levels

    Quote Originally Posted by Beez
    Well, I have no authority to discuss chemistry, so I will defer to those with more expertise on this subject. BUT, my experience with my one pool seems to confirm your assertion. I added borates with the hope that they would help to mitigate the ever rising PH in my pool, but so far I can tell no difference.

    That being said, I have no regrets with the addition because I like what the borates have done to the feel of the water, and I am trusting in their advertised algae-static properties.

    FWIW,
    Dave
    Dave,

    The addition of Borates does NOT normally reduce the amount of acid needed to be added over time. It only slows down the rate of pH rise, but you end up needing to add more acid when it does rise because there is more buffering. I have seen this in my own pool where the pH rises more slowly, but takes more acid to get it back down with the net result being the same amount of acid per time period. No one has claimed that borates, by themselves, reduces the amount of acid you need to add to keep the pH stable. I'm sorry if this wasn't made clear. In spas the effect of 50 ppm Borates is much more dramatic due to the increased aeration there and it makes the use of bleach in such spas tolerable, especially when combined with a lowering of TA.

    The only things that lower the rate of pH rise are a lowering of Total Alkalnity (TA) or turning down the on-time of a saltwater chlorine generator (SWG) or reducing other sources of aeration (or use of a pool cover). The Borates can act as a mild algaecide so for those SWG pools where there is some mild algae growth requiring a higher SWG on-time, then the Borates can sometimes let one lower the SWG on-time and this is what reduces the rate of pH rise (from less aeration for carbon dioxide outgassing and less undissolved chlorine gas outgassing).

    So in your own pool, have you tried substantially lowering the TA level? I believe it's currently at 80 ppm, but have you tried lowering it to 60 ppm to see if that makes any difference (if it does, then for your plaster pool you'd want to have the CH be higher). If you have new plaster, then nothing will reduce the amount of acid needed to keep the pH lower -- any specific base addition to your pool, such as plaster curing, will need acid to compensate and nothing can prevent that. It is only when the source of rising pH is carbon dioxide outgassing that you can control that by lowering TA, reducing aeration sources (waterfall, spillover, fountain) or by using a pool cover. I have a pool cover so that substantially stabilizes the pH in my pool so that I only add a small amount of acid every month or two. Now with borates, the rate of rise is about half as much, but takes twice as much acid (at the same amount of pH rise) so I can either add twice the amount of acid half as often or the same amount of acid as often as before (i.e. but with the pH having risen by a smaller amount) with the net result being the same amount of acid that needs to be added.

    In earlier posts, you mentioned how you turn up your returns to barely break the surface of the water. That's probably not a lot of aeration, but I know that to aerate my pool I have pointed the returns upwards with the pump on high and more substantial breaking of the surface to intentionally aerate when I wanted to lower the TA and this did work. Another factor in your case may be the bleach you are using as off-brand bleach has more excess lye in it, but this is a rather small effect that would account for perhaps a 0.2 or so rise per month. I believe you have been seeing 7.5 to 7.8 in less than a week which is pretty substantial. We really haven't yet figured out the source of this pH rise in your pool. However, if you notice that having a higher pH target results in less acid per time being needed, then that would imply carbon dioxide outgassing as the main source of pH rise so an even lower TA should help. By any chance, do you get regular rains in your area? I know that we had one forum user who lives in Hawaii where the raindrops caused significant aeration and he found that lowering the TA to 50 ppm virtually stopped the pH rise, though that is lower than we would normally recommend (it's OK if you are careful not to have any acidic sources, have some supplemental pH buffering, and/or watch the pH carefully). Another user here found pH stability at a TA of 40, but that's lower than I would recommend though it does show the principle working in practice.

    Richard
    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: Heresy-Borates do not act as a buffer at pool pH levels

    Quote Originally Posted by wejones

    When you dissolve borax in water, you get a weak lewis acid, boric acid and a base tetrahydroxy borate.
    This is a true statement.
    The primary buffering capacity in pools is due to alkalinity. Specifically due to the bicarbonate buffering system. Once you go above pH 6.3 you have a carbonate-bicarbonate buffer until around a pH 8.3.
    You have a carbonic acid/carbon dioxide/bicarbonate buffer system. Carbonates do not enter into it until you are above normal pool pH range.

    This is why alkalinity is one of the most important chemical parameters to maintain in a pool. Alkalinity in our pools is mostly carbonate.
    It is bicarbonate at normal pool pH. You need to review the chemisty of this particular buffer system.

    The other half of the chemical species is not important and is just a counter ion. Carbon dioxide from the atmosphere and the carbonate part of alkalinity form a buffer system. This is a lesson one learns in Indiana since the ground water is typically 250-450ppm alkalinity.
    FWIW, in parts of Florida the TA is often in the neighborhoold of 300 ppm and CH of 600-800 ppm is not uncommon. There are parts of the country (Like Arizona) that routinely deal with CH of 1200 ppm! You cannot make generalizations like you just did. They don't hold water (pun intended). WATER BALANCE is the most important parameter to maintain. You cannot separate out one part and say that is the most important. They all interact!
    Proper maintenance of your alkalinity is the most important aspect of pool chemistry maintenance. You will fight an uphill battle until you get your alkalinity within acceptable ranges for your pool. You will waste time and money until you bring your alkalinity in line and keep it in line.
    Edited for politeness. JasonLion

    Proper TA is an important aspect of water balance but no more important that the others. IMHO, the MOST important thing is th make sure the water is properly sanitized!

    It seems that you have problem with high TA where you live. Those that deal with very high CH might feel that calcium levels are the most important aspects of water balance.
    Perhaps these posts might be interesting to you....
    ta-what-is-it-really-t4979.html
    how-to-lower-ta-t5341.html
    acid-column-myth-t1089.html

    Remember, they are not aimed at chemists so they are simplified but the principles are sound.

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    Bob_Funk's Avatar
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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    I can't begin to argue the chemistry, but I can tell you in the 35 days since I added the borates my pH has not moved from 7.6

    Bob
    I consider myself very lucky I found this site before the pool store found me-pool owner since Nov 2008- Stunningly clear 17,000 gal fiberglass pool, thanks to this site, installed in 1982-24" 3.1sq. ft sta-rite sand filter, 1 hp - 2 speed wisperflo pump-WFDS-4

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    ditto...7.4-7.6 here
    TA set at 80
    SWG runs 3 hrs a day
    return pointed down

    I love borates
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    The way I demonstrate the buffering effect to my customers is this:

    I do a pH test then add a few drops of Base Demand Reagent to the sample in the bloc - the pH rises right away.

    I do the pH test again but this time I add a pinch or two of Optimizer/Supreme/Foundation to the sample to be tested- the number of drops of BDR increases substantially.

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    Please understand that I am not attacking or even complaining about my experience with borates in my own pool, I was only reporting the results that I have seen first hand with PH rise. Furthermore, I haven't completed the changes suggested to me by waterbear, so that may alter my whole scenario.

    Tonight I added both calcium chloride to raise the CH, and MA to lower both PH and TA. I won't know until tomorrow morning what effect I've had, but I'm guessing I'll need to add still more to my CH. I didn't want to use too much calcium on the first go. BTW, my TA was at 70 before adding the MA tonight. I expect it to be down around 60 by tomorrow morning.

    I'm not giving up on the borates at all. Like I said above, I'm happy with the addition, but whatever happens I would never blame anything on the advice I've received here! It's all good...

    Thanks,
    Dave
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Heresy-Borates do not act as a buffer at pool pH levels

    Quote Originally Posted by Beez
    . Furthermore, I haven't completed the changes suggested to me by waterbear,
    They are not magic, just one of many things to help with pH control. Gotta do the whole package.

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