Fighting Algae with Borax

[Tredge]

Going to try and follow the posts in china-shop to get my borates to 50ppm.

Bleachcalc says I will need to add 650oz or 40lbs! (40,000 gallon pool)
Should that be right if I've never added any borax before?

Pretty sure I shouldn't attempt to add that much at once

Any advice on how to go about this?

Thanks in advance

[waterbear]

BleachCalc has an error in the borax section and it underdoses by a large margin. To get to 50 ppm in a 40k pool you will need 150 lbs of borax (sodium tetraborate decahydrate), just slightly over 31 and a half boxes of 20 mule team, and 9 gallons, 1 quart, and 1 pint of muriatic acid to neutalize the pH rise and create the borate/boric acid buffer.
If you use sodium tetraborate pentahydrate (Proteam Supreme, Bioguard Optimizer, Omni Maximizer, Poolife Endure) then you will need 107 lbs and 8 gallons, 1 quart, and 3 ounces of muriatic acid.
Add half the amount of borax, then half the acid, then the rest of the borax and all but 1 gallon of the remaining acid. circulate for about 24 hours and then adjust your pH to 7.6 by adding acid. If you overshoot and the pH goes too low then either add a bit more borax to bring it up or aerate the water.

Edit: made a mistake in the amount needed for 50 ppm with the pentahydrate. 107 lbs will only gety you to 40 ppm. to get to 50 ppm you need 134 lbs and 10 gallons, and 3/4 cup acid!

[CarlD]

31 boxes of Borax and 9 gallons of Muriatic Acid?

Is your problem algae or algae prevention?

If it's algae, just attack it by the usual means. If it's algae prevention, well, enjoy yourself.

For me, regular pool maintenance and weekly dosing with 1-2 oz of PolyQuat does it.

[adesalvo]

It really takes a lot of borax to get to 50 ppm. It may be even higher. In the past I divided the dose into quarters and adjusted the ph with acid after each dose. The thought was to prevent (or decrease) the wild pH swing the borax causes.

I am believe that the water is sharper and more crisp looking with the borates included. This is totally subjective and cannot be proven.

Feel safe doing it...

[Tredge]

I can assume I have 0ppm borates in the water now correct?

Never added any before.....

[waterbear]

If you have never used borax to adjust pH it's a safe assumption. I would pick up some AquaChek (or Proteam) borate test strips. I order my Aquachek borate strips from here:
http://www.diywatertesting.com/

Very fast shipping and good price!