The Great Tetraborate Experiment!

[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.

[waterbear]

Don't forget to get a few jugs of acid and order some borate test strips also!

[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

[waterbear]

Week 4 (1 month milestone)
Been raining heavily for past 2 days and water level in pool and spa both a few inches higher than normal, surprisingly, test results are pretty good! I do notice some effects on my numbers from dilution from the excess water. I collected my samples during a break in the rain this afternoon.
Borates still about 50 ppm....the test strips have division for 30, 50, and 80 and it is much closer to 50 than any other color. I would guestimate that it is just under 50 ppm now. Still within the "good" range and will probably go up when the excess water evaporates.
FC 4.0 ppm (I lowered my SWG output last week after the test and it's also been raining pretty hard the past two days. I really expected the FC to be a bit lower than this after the rains....shame I didn't have time to test it during the week before the rains came.)
CC 0 ppm
TC (oto) looked to be 4 ppm also, more than 3 and not quite 5)
pH 7.7(rechecked this, Used both Ben's kit and Taylor 2005...don't know if it had goneup and the rains brought it down or it's still holding....time will tell)
TA 90 ppm ( I expected this to drop some after the rain...was 110 ppm)
Adjusted alk 70 ppm (CYA also dropped 10 ppm due to dilution from the rain...was 87 ppm)
Calcium 170 ppm (once again dilution from the rain...was 220 ppm)
CYA 60 ppm (rain....was 70 ppm)
Salt 3400 ppm (readout on AuqaLogic)
Salt 3400 ppm Tayor K-1766)
Salt level down once again because of the rain
Pool is still clear and sparkling.

Also tested the spa for chlorine and pH
FC 5 ppm (usually at abut 6-7)
CC 0 ppm
TC (oto) darker than 5 ppm
pH 7.6 (tested this with Ben's kit and Taylor K-2005 also)

I am going to wait for the water level to go down by evaporation before I make any changes to the chemistry. Might have to bump up the TA just a bit by maybe 10 ppm to keep the adjusted alk at aroun 80 ppm. We shall see.
Have also decided NOT to any any acid at this time.
I hope the rains end by Sunday because I need to change the skimmer sock and vacumn. Don't know if the dirt in the pool is from the rains or not....It was pretty clean at the beginning of the week so I suspect that a lot of it is just stuff that washed into the pool.

So far I am very happy that I decided to add the borax to my pool.

[sailork]

Is it possible that the sodium released by the salt cell is being bound by boric acid as it leaves the cell? It seems like that would increase the performance of the SWG by reducing the amount of chlorine that binds back to the free sodium in the water. If the SWG is having to work less, then obviously the pH of the pool will rise less slowly as well.

On the otherhand, maybe it's just been too many years since i took chemistry.

[chem geek]

Is it possible that the sodium released by the salt cell is being bound by boric acid as it leaves the cell? It seems like that would increase the performance of the SWG by reducing the amount of chlorine that binds back to the free sodium in the water. If the SWG is having to work less, then obviously the pH of the pool will rise less slowly as well.

Nope, that doesn't make sense chemically. First, sodium is not released by the salt cell. The salt cell doesn't do anything with the sodium ions that are in the water, except that they help the conductivity of the water itself to help carry (balance) charges from one plate to the other. The salt cell simply converts chloride ion into chlorine gas and this chlorine gas dissolves in the water to produce disinfecting chlorine (HOCl). See this post or this post for more technical details.

The main way that Boric Acid (borates) may help reduce chlorine consumption is in inhibiting algae growth. It is well known that Boric Acid will inhibit algae growth (see this link) so with less algae growth, there is less algae for chlorine to kill or deactivate. I am surprised that this results in a measurable decline in chlorine usage since I didn't think the killing of algae in "clean" pools consumed very much chlorine at all, but I could be wrong. I thought that the bulk of the chlorine consumption was from the breakdown from sunlight and I doubt that Boric Acid has anything to do with reducing that process, though if it does (which I believe is unlikely), then I have the concern that it might operate the way that CYA does and bind to the chlorine making a new compound that is essentially ineffective as a sanitizer.

Richard

[sailork]

Doh! I really was forgetting my basic chemistry!

[Spensar]

Found this link in some old bookmarks. I haven't used them, am not related, etc., but it is an interesting site that sells bulk chemicals, including borax. You can get a 55 pound bag for $1.35/lb. + shipping. Not sure how this stacks up with 20 mule team on sale, but you won't have all those boxes.

http://www.chemistrystore.com/borax.htm