Borax as algaecide - trying to find info

What is floc, clarifier, stabilizer, cyanuric acid,
algaecide, brightener, dichlor, sodium hypo,
sodium bisulfate, ....??
Ziora
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Borax as algaecide - trying to find info

Postby Ziora » Mon 10 Sep, 2007 19:46

IG 16x32, sand filter, vinyl liner. Approx. 20,000 gal.

I have been using 4 oz. of PolyQuat 60 per week, but ran out. I read somewhere about using Borax, but can't find the post. Can someone please point me in the right direction, or share the info on it's usage?

TC 13
FC 13
pH 7.6
TA 85
CH 25
CYA 10-20

Lots of rain and weeks of triple digit heat took it's toll. This is the second day of shocking and there is no algae right now. I used some dichlor I had on hand to raise the CYA and lower the pH a little. I wasn't getting a CYA reading before.


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Postby chem geek » Mon 10 Sep, 2007 23:17

The long thread that talks about using Borates is here and the bottom line is that adding Borates to the pool in the quantity of around 30-50 ppm will act as an algaecide, though it does not seem to be quite as effective as a weekly maintenance dose of PolyQuat 60. It basically helps, and lowers chlorine consumption, but isn't a surefire preventative if the chlorine gets to zero for some reason. Also, that level of Borates in the pool is at the edge of first-symptoms toxicity for animals such as dogs IF they drink from the pool every day (about a quart per day for a medium sized dog).

Borax will raise the pH so if you want to get to 30-50 ppm Borates, you add a lot of both 20 Mule Team Borax and Muriatic Acid so that the pH remains stable. The Borates will also act as an additional pH buffer which is especially useful for users with an saltwater chlorine generator (SWG) that tends to make the pH rise.

If you maintain chlorine levels at a minimum of 7.5% of the CYA level, with a normal manually dosed target of at least 11.5% of the CYA level (for a cushion of error) then that is sufficient to keep your pool free of green algae. The algaecide would just be insurance in case the chlorine level dropped for whatever reason. If you don't watch your CYA levels (so they climb from continued use of Trichlor or Dichlor), then the algaecide is essential. In your situation, it sounds like you have been using bleach or chlorinating liquid so have been in pretty good shape. Why were you shocking the pool? If it was because you had algae, you need to maintain shock level (40% of the CYA level) until the following three things all occur: 1) the water is crystal clear, 2) there is no more than a 1 ppm FC overnight drop in FC level, 3) there is no more than 0.5 ppm Combined Chlorine (CC). I'm guessing that if you didn't have CYA before, then the chlorine could have gone to near zero quickly in sunlight and that led to algae, right?

Another alternative to using algaecide is using a phosphate remover. This can be expensive, depending on the level of phosphates in the pool, but needs less frequent maintenance doses, depending on how often phosphates rise in the pool.

Richard
Ziora
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Postby Ziora » Tue 11 Sep, 2007 16:13

Yep, you are right. I got algae because the chlorine dropped to 0 a few times due to lack of vigilance. I forgot to add it once and left it in someone elses care a few times. I also didn't keep an eye on the CYA.

Amazing how fast things can turn ugly when you get lazy.

I guess using the borax as an algaecide isn't right for me. I want the extra help the PolyQuat gives if the chlorine drops too low. I still added 72 oz. today because I read another post somewhere that a little borax makes the water sparkle more and gives a silky feeling to the skin. I'm not sure what level that person got their water to, but according to the bleach calc, 72 oz. will raise my borates to 11.6ppm. I'll use pH Down instead of muriatic acid. I've never used it....afraid of it, quite honestly.
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Postby chem geek » Tue 11 Sep, 2007 17:29

pH Down, which is dry acid aka sodium bisulfate, adds sulfates to the water. A little bit is not a problem, but if you use it as your sole source of acid and add it frequently, then the sulfates can build up. Unfortunately, though there is evidence of sulfates being harsher on some pool and deck surfaces, I don't have any good numbers for exactly what level that would be.

There are some half-strength Muriatic Acid formulations that fume a lot less, but unfortunately they cost about the same per volume so are effectively twice as expensive.

Richard
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Postby Ziora » Tue 11 Sep, 2007 19:05

Another bit of info. I have to consider. I don't remember reading about sulfates when I was clearing up my pool. I'm also completely ignorant when it comes to muriatic acid...best way to store it, safe handling, safety precautions, etc.

I was thinking it would be a pain to get my TA adjusted after adding it.

Seems like I'll be faced with something distasteful no matter what I choose. Oh well, no time like the present to start learning how to use it.

Edited to add: Yes, I use 6% clorox, the strongest available in my state. I was told it was because some pool company had a big explosion, so anything stronger is banned in GA.
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Postby chem geek » Tue 11 Sep, 2007 22:00

Bleach and chlorinating liquid won't explode and aren't even flammable. They are mostly water.

It's Cal-Hypo that is flammable and the most dangerous form of chlorine (other than chlorine gas which isn't available for residential pools). It makes no sense for there to be a ban in the state for chlorinating liquid. It's probably just that the local dealers don't see enough volume to carry it or perhaps there isn't a local supplier so the interstate costs are higher.

Richard
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Postby Ziora » Tue 11 Sep, 2007 22:28

I broke my thermometer in chemistry class and it was downhill from there.

Thanks for the info.

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