The Great Tetraborate Experiment!

[chem geek]

OK, I finally put in the full Boric Acid equations into my spreadsheet and here's what I found out (assuming I didn't make an error). [EDIT] I initially made a mistake, but have corrected it and corrected the numbers below. [END-EDIT]

One box of 10 Mule Team Borax which you say is 4 pounds and 12 ounces (76 ounces total) and which I've been told is sodium tetraborate decahydrate, will add 9.78 ppm Borate (measured as ppm Boron) so it would take about 5 boxes to get to 50 ppm.

So, to get to 50 ppm in your 6,600 gallon pool, you need 388.6 ounces (24 pounds, 4.6 ounces -- or about 5 boxes plus 8.6 ounces) and 193.9 ounces (1 gallon, 8 cups, 1.9 ounces) of Muriatic Acid or 1.19 quarts per Borax box (you should alternate adding some Borax and then Muriatic Acid back and forth so as not to wildly swing your pH in your pool). This will increase your TA by 7.0 ppm CaCO3 equivalent and will increase your TDS by 416.1 ppm (77.0 from chloride ions from the Muriatic Acid and 339.1 from Sodium and Boric Acid from the Sodium Tetraborate) though some of this TDS increase (about 270 ppm) will not generally be seen in TDS measurements because some of this increase is with the neutral ion B(OH)3 and the standard TDS measurment is made using a conductivity test (which does not measure neutral ions).

It would appear that the rise in TA with Borax is more like a 7:1 ratio of ppm Boron to TA rise, not the 3:1 that Proteam claimed. The 7:1 is also consistent with my earlier calculation, but then I'm the same person doing both calculations so I certainly could have made the same mistake twice!
Perhaps the relatively small increase in TA is why you didn't notice it. It's less than 1 drop on the TA test and you had other things going in your pool in the meantime.

As for the buffering ability of 50 ppm Borate (Boron) in your pool, here's an example. Let's say that we use your numbers and have 2 moles (about 4%) of the total carbonate in your pool outgas as carbon dioxide. This would cause the pH to rise from 7.6 to 7.86 with no Borates in your pool. With 50 ppm Borate, the pH rise is only from 7.6 to 7.71 which is much less. It appears that the Boric Acid / Borate buffer system is quite efficient and is a good compliment to the Carbonate buffer system without having the side effect of outgassing carbon dioxide. [EDIT] Remember that TA is measured in ppm CaCO3 (100.0892 g/mole) while Total Borates are measured in ppm Boron (10.8117 g/mole) and that CaCO3 counts twice for alkalinity (because it can consume two hydrogen ions). So the Total Borates measured in the same units as TA would be 100.0892/10.8117/2 = 4.63 times larger so 50 ppm of Borates has a buffering equivalent closer to 230 which is why it is so effective (it doesn't increase measured TA by that much because most of it is Boric Acid which is uncharged -- this just shows that TA isn't really a measure of buffering capacity unless you use carbonates at a typical pool pH where the HCO3- species dominates). [END-EDIT]

This means that you should be able to run your pool with much lower TA and still get good buffering. For example, you can lower your TA to 80 and without the 50 ppm Borate your pH would rise to 7.97 but with 50 ppm Borate it would only rise to 7.73 so about the same as with the higher TA.

Richard

[waterbear]

OK, I finally put in the full Boric Acid equations into my spreadsheet and here's what I found out (assuming I didn't make an error). [EDIT] I initially made a mistake, but have corrected it and corrected the numbers below. [END-EDIT]

One box of 10 Mule Team Borax which you say is 4 pounds and 12 ounces (76 ounces total) and which I've been told is sodium tetraborate decahydrate, will add 9.78 ppm Borate (measured as ppm Boron) so it would take about 5 boxes to get to 50 ppm.
I put in six and it was a bit high. (I thought it might be before I did it) My initial calculations came to about 5 boxes and 2 lbs more (25.75 lbs) but I was not anywhere near as precise as you and based them on Proteams dosing chart and ajusting the weight of the decahydrate as 1.3 more than the pentahydrate needed. I was ballparking the whole way. I also started with an initial borate reading of 15 ppm and my testing is limited by the accuracy of the test strips...not great but it certainly got me in the ballpark pretty easily!
So, to get to 50 ppm in your 6,600 gallon pool, you need 388.6 ounces (24 pounds, 4.6 ounces -- or about 5 boxes plus 8.6 ounces)
Pretty close to what I came up with when I looked at my calculations more closely ! I got about 23-24 lbs!
and 193.9 ounces (1 gallon, 8 cups, 1.9 ounces) of Muriatic Acid or 1.19 quarts per Borax box
In actual practice I used 1 1/4 qts acid per box to keep the pH in line....It's pretty close. I was going for measurements that were easy to do.
(you should alternate adding some Borax and then Muriatic Acid back and forth so as not to wildly swing your pH in your pool).
Which is what Proteam recommends....add 3/4 gal acid and then 10 pounds of the pentahydrate...I added 1/2 gal and 2 boxes at a time....and found that I needed to add more acid... probably would have been right on the money if I added about 2.5 quarts and 2 boxes at a time. I added the acid and put the borax in a 5 gal pail of water and added it to the pool and brushed. It dissolved almost instantly once added to the pool. Pump was running the whole time. If I didn't have a SWG I would have just added the borax to the skimmer but I have found in the past that adding borax or baking soda to the skimmer trips the high salt sensor on my SWG and I have to reset it.
This will increase your TA by 7.0 ppm CaCO3 equivalent and will increase your TDS by 416.1 ppm (77.0 from chloride ions from the Muriatic Acid and 339.1 from Sodium and Boric Acid from the Sodium Tetraborate) though some of this TDS increase (about 270 ppm) will not generally be seen in TDS measurements because some of this increase is with the neutral ion B(OH)3 and the standard TDS measurment is made using a conductivity test (which does not measure neutral ions).

It would appear that the rise in TA with Borax is more like a 7:1 ratio of ppm Boron to TA rise, not the 3:1 that Proteam claimed. The 7:1 is also consistent with my earlier calculation, but then I'm the same person doing both calculations so I certainly could have made the same mistake twice!
Perhaps the relatively small increase in TA is why you didn't notice it. It's less than 1 drop on the TA test and you had other things going in your pool in the meantime.
Right in line with Proteam saying that 30 ppm will cause a 10 ppm increase in TA. Drop based kit might or might not show an increase since the precesion is 10 ppm.
As for the buffering ability of 50 ppm Borate (Boron) in your pool, here's an example. Let's say that we use your numbers and have 2 moles (about 4%) of the total carbonate in your pool outgas as carbon dioxide. This would cause the pH to rise from 7.6 to 7.86 with no Borates in your pool. With 50 ppm Borate, the pH rise is only from 7.6 to 7.71 which is much less. It appears that the Boric Acid / Borate buffer system is quite efficient and is a good compliment to the Carbonate buffer system without having the side effect of outgassing carbon dioxide.

This means that you should be able to run your pool with much lower TA and still get good buffering. For example, you can lower your TA to 80 and without the 50 ppm Borate your pH would rise to 7.97 but with 50 ppm Borate it would only rise to 7.73 so about the same as with the higher TA.

Richard

I will continue running my pool with the ajusted alkalinity at 97 ppm and see how long the pH remains stable and if I can repeat the results before I lower the ajusted alk to around 80. then I will see how it goes with the lower alk. I intend to post my results weekly. So far I think the addition of borates is a good idea. It certainly is not an expensive experiment when done with 20 mule team. It has only cost me about $35 for the 6 boxes of borax, 2 gallons of acid, and borate test strips!

Now if there was any way to test whether it really has algaestatic properties without my having to turn off the SWG and see how long it takes for my pool to go green I would do that also! Maybe when it gets too cold to swim I will try it. Nothing a few gallons of bleach can't cure!

So far I feel that the experiment has been a success but it is still early into it.
It might be useful to simplify the measurements if anyone else cares to try it.
If I have not made an error 1 box (76 oz) of borax will raise 1000 gallons approx 50 ppm ( slighly higher actually) and will need 5 cups of acid to get the pH back into the proper ballpark. Does this seem like a good way to dose or will it create too large an error on a very large pool? I think the key is to figure out a simple and easy way to meaure the dosage of both the borax and acid. Richard, your thoughts would be appreciated!

[chem geek]

If I have not made an error 1 box (76 oz) of borax will raise 1000 gallons approx 50 ppm ( slighly higher actually) and will need 5 cups of acid to get the pH back into the proper ballpark. Does this seem like a good way to dose or will it create too large an error on a very large pool? I think the key is to figure out a simple and easy way to meaure the dosage of both the borax and acid. Richard, your thoughts would be appreciated!

I get that 1 box (76 oz) of Borax (decahydrate) will raise 1000 gallons by 64.54 ppm which is quite a lot more than the 50 ppm you quoted. I don't think an error of 10% is a huge deal, but this is a bit beyond that (about 15%). This 1 box of Borax also requires 38.56 oz. of acid or 4 cups, 6.56 oz. That's pretty close to 5 cups to be accurate enough.

I'm glad your experiment was a success. The improved buffering alone is a good reason to use borates (boric acid) as fighting a rising pH seems to be the biggest problem most people have. However, it would still be necessary to lower the TA to reduce the acid demand. Though the borates will have the pH rise less, the amount of acid needed to restore pH when it does rise is the same as it would have been without borates.

As for testing the algicidal properties, you could just use a large tub or basin for your test, rather than the entire pool. Of course, the quantities of chemicals you would use would be rather small, but you could also "enhance" the likelihood of developing algae by adding a small amount of nitrates and phosphates to this tub/basin and you could find some algae to dump in as well (if you have any around). That would certainly be a vigorous extreme test! Ideally, you would have two tubs/basins so one would have the borates and the other wouldn't and you'd add the same amount of other stuff to both (and keep both in the sun, keep the water warm, etc.).

Richard

[waterbear]

I get that 1 box (76 oz) of Borax (decahydrate) will raise 1000 gallons by 64.54 ppm which is quite a lot more than the 50 ppm you quoted. I don't think an error of 10% is a huge deal, but this is a bit beyond that (about 15%). This 1 box of Borax also requires 38.56 oz. of acid or 4 cups, 6.56 oz. That's pretty close to 5 cups to be accurate enough.
If my math is correct than 3lbs 12 oz should raise 1000 gallons 50 ppm and would need 4cups (1 qt) acid to ajdust the pH.
I

Does this sound right to you?

[chem geek]

Yup, that's right. [EDIT] It's actually 3lbs 11 oz to raise 50 ppm in 1000 gallons and needs 30 ounces (3 cups, 14 ounces) of acid to compensate. Just being anal-retentively accurate! [END-EDIT]

[waterbear]

This weeks test results (week 3):
(I have added my nromal amount of water to make up for evaporation each week, btw. I add it after I test...my normal procedure)
Borates 50 ppm
FC 5.5 ppm NO CHANGE (I lowered my SWG output again after the test and will see where I end up in another week. I had already lowered it last week. One of the claims made for tetraborates is less chlorine usage. I thought it was just marketing hype but maybe not....we shall see.)
CC 0 ppm
pH 7.7 (this is REALLY amazing, last week was 7.6! By the end of 3 week my pH is 8.0 and this is when I usually add my acid to bring it down! I rechecked the pH several times with 3 different kits just to make sure and even used the acid and base demand reagents to make sure the color was where I thought it was! I am going to leave it here and see if it increases anymore in a week.

TA 110 ppm (I have had the spillover and waterfalls running almost constantly last week for the kids and the TA did not move and this is 10 ppm from last weeks test of 120 ppm and that is also the accuracy of the test. As far as I am concerned this is NO CHANGE. I did not bother to repeat this test....close enough for government work, as they say
Adjusted alk 87 ppm NO CHANGE (see TA test results)
Calcium 220 ppm NO CHANGE
CYA 70 ppm NO CHANGE
Salt 3700 ppm (readout on AuqaLogic)
Salt 3600 ppm Tayor K-1766)
Pool is still clear and sparkling.
Now this is proof enought for me that the borates have helped to buffer the water. I will continue to report weekly and see what happens. I am particularly interested in my chlorine readings. I have my SWG down to 6% from 15% output in 3 week, normally it's at 10% and maintains about a 4 ppm FC. I raised it to 15% because we got a lot of rain and last week I lowered it back to 10%. Richard, your thoughts on this?

Didn't bother retesting phosphates, I know they are off the scale! (between 2000-3000 ppb).

One thing I have noticed, usually every 3 weeks is when I need to vacumn the pool because stuff collects near the main drain. It didn't need it today. Gonna wait another week and see. Also the skimmer sock usually needs to be changed out every week....this is the second week on the same sock...just took some leaves out of the skimmer. Don't know if this is from the borax or not but it was interesting since I KNOW my pool and what it normally requires. As Alice said, "Curiouser and Curiouser!" (Come to think of it, the pool is so clear it sort of looks like a 'Looking Glass'.

[chem geek]

TA 110 ppm (I have had the spillover and waterfalls running almost constantly last week for the kids and the TA did not move and this is 10 ppm from last weeks test of 120 ppm and that is also the accuracy of the test. As far as I am concerned this is NO CHANGE. I did not bother to repeat this test....close enough for government work, as they say

I have my SWG down to 6% from 15% output in 3 week, normally it's at 10% and maintains about a 4 ppm FC. I raised it to 15% because we got a lot of rain and last week I lowered it back to 10%. Richard, your thoughts on this?

Evan,

WOW! Maybe the borates will cure cancer! Seriously, I'm very impressed with your results. I (as usual) have a few comments -- take them for what they are worth.

Regarding the TA, though the Boric Acid will buffer the pH, I don't see how it affects changes in TA (carbon dioxide outgassing), at least not directly. It is true that increasing your total borates (ppm Boron) to 50 and adding acid to keep your pH the same at, say, 7.5 actually increases your TA by 6.1 (11.7 at pH 7.8) due to additional relatively small amounts of borate ion dissociated from the boric acid. This increase in the TA is not carbonate, however, and I calculate no change in CO2 outgassing. Besides, with your current numbers, your CO2 outgassing rate is down to 4.0 which is very small so I would expect your TA to be relatively stable.

Now for the chlorine usage question. I don't know why the Boric Acid would cut down the chlorine usage. If you can, try to see if this usage is cut down both day and overnight or if it seems to be mostly a reduction (percentage-wise) in daytime usage. I'm trying to figure out if the Boric Acid is helping to protect the chlorine from sunlight or if it is helping to disinfect and/or oxidize so that chlorine doesn't have to. I don't see the mechanisms for Boric Acid in either process, but it would be good to isolate down to one of these. Since most chlorine usage is due to breakdown from sunlight, it is more likely that the Boric Acid is helping there somehow, but I don't know the mechanism and if it helped prevent breakdown in the same way that CYA does (by binding with chlorine), then that would likely also lower chlorine's effectiveness which wouldn't be good. So we really do need to get to the bottom of this.

Richard

[cgc2]

[QUOTE=waterbear;34007]I will continue running my pool with the ajusted alkalinity at 97 ppm and see how long the pH remains stable and if I can repeat the results before I lower the ajusted alk to around 80. then I will see how it goes with the lower alk. I intend to post my results weekly. So far I think the addition of borates is a good idea. It certainly is not an expensive experiment when done with 20 mule team. It has only cost me about $35 for the 6 boxes of borax, 2 gallons of acid, and borate test strips!


In process of converting a 29k pool now...figuring close to 20 - 23 boxes for a 50 ppm...I will start with 15, and work my way up from there. Test strips should be ready for my pickup on Monday.

So far, 10 boxes, 2.5 gallons acid in pool that had readings of ph 7.4, TA 80 (unadjusted..69 adjusted), ch 360, cya 40 and building up to 70ppm, Salt 3000ppm and may add another bag.

Water sparkles and is very clear...going to take a test dip.

[bizbad]

Waterbear I really dont know how you keep the borates high enough, every time I add Borax it rains and I need to add more. I have given up. I would be adding Borax twice a week and it would just take the place of the acid I have to add every two days. I am glad it seems to be working for some of you, but I have had no luck. I get to the 50 ppm and it rains and I am back down again. I think I will just keep adding acid and occasionally buy some polyquat 60. I think its an even trade.

[waterbear]

If you are draining water when it rains then the borate levels will go down, along with the rest of your water balance going 'off'. If you just let the water evaporate then the levels will go back to where they need to be. If your pool is overflowing from the rain then you will lose not just borates but also other levels in your pool will be off, CYA, Salt, chlorine, TA, CH, all of them! How are you testing your borates. Also realize that they just need to be between 30-50 ppm so if they are not exactly at 50 ppm then I would not worry too much about it. If you had a SWG you would be having exactly the same problem with your salt levels, btw. You would also have the same problem with CYA if you are using an unstabilized chlorine source and adding CYA to your target ppm so I don't really understand why you are having problems maintaining the borates.