Borates Experience

[chem geek]

I added 50 ppm Borates to my pool last year. It seems to reduce the surface tension of the water (less of a meniscus in vials when testing) and seems to make the water sparkle more. I definitely noticed that the water is far less reactive to algae growth -- I've had >3000 ppb phosphates in my pool so I've had to be careful to maintain the chlorine properly as algae can grow quickly if I don't, but since the borates I did an an experiment letting the chlorine get low and didn't notice anywhere near the same rate of dull/cloudy water development for a pending algae bloom.

I've never had a pH rise problem in my pool so didn't notice much change there -- borates are an additional pH buffer. It does seem that the pH rises more slowly and needs more acid when I do need to add it, but the result is the same total acid per unit time, just more quantity added less frequently.

As waterbear mentioned, many people have tried it and most think it's great though there are a small number who saw no benefit from their perspective.

Richard

[BigDave]

Thanks, I read through the Great Tetraborate Experiment a while ago when I was still lurking around here. Lately I've noticed that Waterbear regularly recommends borates and recall that PoolDoc recommended borates for someone battling metal problems / staining. The positives are very attractive to me and relatively easy to try in our small pool. I remember some of the China Shop conversation regarding the safety of ingesting borated(?) pool water. Is there a consensus regarding safety for dogs and people? I'm not sure I can keep the young'ns from drinking some of the pool.

[chem geek]

I wrote about borates safety in this thread.

[BigDave]

Wow! Thanks!
Research is way better than consensus (but takes a lot longer to read).

I see that research referenced in the WHO report indicated that 50mg/ml borate should be effective in supressing / eliminating several of the algae species studied as has been experienced by many. Why, I wonder, would the borate pool product providers label thier product dosage (from the EPA report) at ten times that rate? Is the idea to use boron as the primary sanitizer?

I'm not sure I can stop the kids (mine and others in the neighborhood) from drinking a tablespoon a day no matter how much I insist. I suspect somebody pees in it (CC spikes) even though I personally look each swimmer in the eye and say "The potty's just through the door, not in the pool". On the other hand, they don't swim every day and we only have a pool in the summer and the research suggests chronic exposure is more of the problem than acute episodes ("Sorry Dad, I didn't mean to drink a half gallon of pool water, I was thirsty").

I think I'll try it next summer - almost time to drain, dry, fold, and store.

I am still interested in anyone else's experience with borates positive, neagtive, or neutral.

[waterbear]

Wow! Thanks!
Research is way better than consensus (but takes a lot longer to read).

Why, I wonder, would the borate pool product providers label thier product dosage (from the EPA report) at ten times that rate? I

Simply because the research done in their test pools (here in St. Augustine by John Girvan, in fact, when he owned Proteam and before they were bought by Haviland and later by Biolab) determined that maximum algaecidal benefits (for the type of algae that normally grows in pools) were obtained at 30-50 ppm for chlorine and bromine and 50-80 ppm for biguanide santized pools.
Here are a few of the original patents:
http://www.poolsolutions.com/arc/pat...04,594,091.htm
http://www.poolsolutions.com/arc/pat...05,131,938.htm
http://www.poolsolutions.com/arc/pat...05,478,482.htm ("oxybor" patent)

[chem geek]

Why, I wonder, would the borate pool product providers label thier product dosage (from the EPA report) at ten times that rate? Is the idea to use boron as the primary sanitizer?

I don't know where you are getting the "ten times that rate" -- are you implying that the product dosages are 500 ppm which is 10x 50 ppm? That isn't true. Remember that the borates measurement is in ppm Boron with a molecular weight of 10.812 g/mole and not in ppm Boric Acid at 61.83 g/mole or sodium tetraborate pentahydrate at 291.29 g/mole.

As for the tablespoon limit, that includes a safety factor of 100 since no studies were done on humans, only on other animals (rats, dots, etc.) and as you point out it's a chronic limit for regular drinking since the body does process boron and in fact it's an essential nutrient. You just don't want to overwhelm your body with it. In practice, I think the borates at 50 ppm are safe for humans in pools and even for children who may occasionally gulp some water. It would be more of a concern for dogs drinking lots of water every day from the pool -- mostly getting close to the edge of first symptoms (shrunken testicles in male dogs).

[BigDave]

I guess I misunderstand - highly likely.

As I understand, the last paragraph on page 9 of the EPA report describes product labeling that recommends "4.5 lb ai per 1,000 gallons (540 mg/L pool water concentration), 4 lb ai per 1,000 gallons (480 mg/L pool water concentration)" which I took to mean 540ppm and 480ppm or about 500ppm Boron. I assumed that this value was Boron as it is used to calculate Margin of Exposure and is compared to other sources of boron in the environment.

The report goes on to say (page 14) that the "Sodium borate applications to swimming pools and spas resulted in unacceptable risks for some of the higher boron concentrations in pool water (e.g., concentration in water of 480 mg/L and 540 mg/L); however, the lower concentration of 240 mg/L did not result in risks of concern. Therefore, the end-use product labels for swimming pool products must be revised to delete application rates above 240 mg/L. Registrants have agreed to amend their labels by removing the higher application rates to Agency acceptable levels."

It wasn't clear to me why the label dosage would be so high when algae would be effectively clobbered at a much lower level.

I apologize for my bad chemistry, I thought I understood the reports - Doh!

[chem geek]

Don't worry about making the mistake. It took waterbear and I a while to figure out that the units were ppm Boron. It took me a year before I figured out that chlorine was measured in ppm Cl2 units. These things aren't obvious until you see them defined somewhere.

4.5 pounds is 2.041 kilograms and 1000 gallons is 3785 liters so that's about 540 mg/L of sodium tetraborate pentahydrate which is 291.29 g/mole. There are four boron that result from this compound with each at 10.812 g/mole so this amount of product produces 80 mg/L Boron or what we call Borates.

I think the EPA report was saying that some products recommended dosages that were too high, but that's not the example given above. As for why some products used such high dosages, one reason is that not all algae are killed at 50 or even 80 ppm borates though most algae are inhibited at that level. Another reason is that higher borates levels provide greater pH buffering.

Current products such as ProTeam Supreme use 2 pounds per 1000 gallons for around 35 ppm Borates which is in their 30-50 recommended range.