The Great Tetraborate Experiment!

[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

[chem geek]

I ran into this little tidbit

Borates are used to lower the pool's requirement for chlorine, by depriving algae of abundant quantities of dissolved carbon dioxide. The lowering of the carbon dioxide levels will slow algae growth and reduce the chlorine consumption.

from this webpage and if it is true that algae depend on abundant quantities of dissolved carbon dioxide, then this could explain reduced chlorine usage IF you had algae in your pool using up your chlorine. I suppose that there may always be some algae dropping into your pool, but I didn't think it was that much nor that it ate up that much chlorine (except during a bloom which you then have to shock).

Also, you have to lower your carbonate alkalinity to get this benefit. This would also lower the tendency in the pH to rise (beyond the buffering effect) and would reduce acid demand. Essentially, the borates let you use a non-carbonate pH buffer in your pool so you can run at a lower carbonate level that apparently helps prevent algae and certainly lowers the outgassing of carbon dioxide with its resultant pH rise and acid demand.

So though the website claims that borates reduce the amount of dissolved carbon dioxide in the water, I believe this is only true if you let the carbonate alkalinity get lower which you might "naturally" do by lowering the TA after its rise from adding so much Borax. HOWEVER, as far as dissolved carbon dioxide being reduced, you would have to have your carbonate alkalinity reduced a whole lot more, I would think, since cutting TA in half will only cut the carbonate alkalinity by a little more than half (with water balance turning more corrosive, though probably still in the OK range). It's still an intriguing thought.

[EDIT] After thinking more about it, I don't think the "reduced dissolved carbon dioxide" theory is the answer. Consider ponds and lakes that have algae in them. They are probably closer in balance with the air for dissolved carbon dioxide and that means they have quite a bit less than pool water unless the water is extremely alkaline. It seems to be common wisdom that Boric Acid suppresses algae in pools and that it interrupts photosynthesis in plants (probably does the same to algae, since the kinds of algae found in pools are plants). This WHO document gives more details. Interestingly, smaller amounts of borates (10 ppm) actual stimulated certain kinds of blue-green algae growth, but growth was inhibited at 50 ppm or above with 100 ppm inhibiting more growth (so perhaps this is a more effective level to use??? -- but these tests were done in simulated sea water which is not the same as pool water). [END-EDIT]
Richard

[waterbear]

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

I will try but I am working two jobs and taking classes so I really only have time to test my water on Fridays. I will see if I can get a chance to do some spot checks in the AM and at night (I don't usualy get home from work until around 1 AM so I don't know if they will do much good). This might have to wait until next summer. I suspect that the known anti fungal action of boron might have something to do with this. Perhaps the boron is killing some of the nasties in the water so the chlorine doesn't have to?

[sailork]

Fine. That's it. I'm dumping enough boric acid in my pool to drop the pH to a normal level and bring the borates up to at least 50ppm. The only questions are where do I get the boric acid, how much do I add and will it hurt my DE filter if I dump it in the skimmer?

[waterbear]

Sailork,
It really is much easier (and probably cheaper) to use borax and muriatic acid. They will neutralize each other and produce boric acid/borate buffer in the water and some salt. Just put in 5 cups of acid and pour a box of borax into the skimmer and repeat until you have reached your level. IF you go through this thread you will find where Richard has worked out the dosage for 1000 gal to reach 50 ppm and I gave a close approximation with easier measurements. Don't forget to get some borate test strips....I got mine online from
http://www.diywatertesting.com/aquachek_borate.html
They arrived in about 4 days and it was the cheapest price I could find...free shipping too.

Boric acid is not very soluable, if I remember my chemistry correctly. and you might have a problem geting it to dissovle...and also, if it lowers the pH too much you will need to add borax and that will raise your boron levels even higher.

[sailork]

Thanks Evan, I've done some digging around on wikipedia etc and they do mention that boric acid isn't terribly soluble in water. You mentioned that some of the stuff you carry at the pool store contains boric acid. Any idea what they might be doing to get it to dissolve?

[waterbear]

These products are meant as weekly or montly additions to replenish the borate level lost by backwashing, splashout, etc. in a pool that already has the required amount of borates in the water. They are used in very small quantities and consist of mostly tetraborates and boric acid or tetraborate and sodium bisulfate (dry acid, pH increaser)
The dosage for the Proteam product (which is sodium tetraborate and sodium bisulfate) is only 4 oz per 10000 gallons at a time!
The NaturalChemistry Salt Water Magic Monthly treatment contains only 1-10% boric acid by weight according to the MSDS for it!

[sailork]

Richard, I've never understood how we can tell how much chlorine is lost through direct action of sunlight and how much is consumed by algae. Given that algae photosythesize I've always assumed they consume most of their chlorine when the sun is shining...

What am I missing? I suppose we could measure CO2 levels during the day and that would give us some kind of guesstimate of photosynthesis?

[sailork]

Ah, thanks Evan. I was thinking something like the methods people use to add CYA would be adequate. I'm pretty sure boric acid is available cheap, but I don't have any idea what might be added to it. Maybe I'll just go to bed and buy a bunch of borax in the morning.

[chem geek]

Richard, I've never understood how we can tell how much chlorine is lost through direct action of sunlight and how much is consumed by algae. Given that algae photosythesize I've always assumed they consume most of their chlorine when the sun is shining...

I am basing my assumption from the experience of users in the algae threads where it appears that algae continue to consume chlorine overnight and that when this stops (which is some time after the water is no longer green and is either cloudy and getting filtered or is near clear), then this means the algae is all killed.

The algae continue to metabolilze (though possibly at a lower rate) at night -- it's just that they oxidize stored organics and "exhale" (so to speak) CO2. During the day, the algae use photosynthesis to build up the organics as "food" and take in CO2 in this process and "exhale" O2.

The oxidation of nitrogenous organics and ammonia also occurs both day and night. So the overnight rate may underestimate the non-sunlight sources of chlorine consumption due to lower chlorine usage from algae algae at night vs. day, but it will at least give one some minimum number to work with.

Richard