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Help With Borates


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Thanks to the experts on this forum, I've been maintaining my 365 gal. spa for the last 4 months without too much trouble. Yesterday I did my first drain/refill and added 2.5 oz. of 20 Mule Team Borax. I calculated this amount based upon 100% purity to reach 50 ppm but I have no way to measure borates and the box does not specify the purity. I suspect I may need more but do not know how much.

Any help appreciated.

I am on a slow dial-up connection so I can't surf around too much but would like to get my water balanced and ready to use ASAP.

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Also, does the addition of Borax change the Alk or CH of the water?

The water is currently at Ph 7.7, CH 150, Alk 60 after a bunch of cycles of muratic acid/aeration. The Ph appears to have almost stabilized but previous experience tells me it will creep up a bit more which will require more acid and lower the Alk further.

I wonder if I need more borates or more calcium.

Thanks!

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I'm assuming you added acid as well as Borax, correct? Borax will significantly raise the pH and cause severe scaling if you do not alternate with adding acid (i.e. split up the dosing and alternate between acid and Borax). If you use Boric Acid instead of 20 Mule Team Borax then you don't need any acid as boric acid is only slightly acidic. Use The Pool Calculator to calculate dosages. In 365 gallons it would take a combination of 21 ounces of 20 Mule Team Borax with 10 fluid ounces of full-strength Muriatic Acid (again, split dosages, do NOT add all at once) OR it would take 14-15 ounces of boric acid.

I believe in your calculations you are using the weight of borax itself, but Borates are measured as ppm Boron which is a much smaller unit of molecular weight so to get to 50 ppm you need a much larger weight of Borax itself (as well as acid). This explains why your pH didn't shoot through the roof -- you added relatively little Borax.

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I'm assuming you added acid as well as Borax, correct? Borax will significantly raise the pH and cause severe scaling if you do not alternate with adding acid (i.e. split up the dosing and alternate between acid and Borax). If you use Boric Acid instead of 20 Mule Team Borax then you don't need any acid as boric acid is only slightly acidic.

Yes, I did add acid and thank-you for your timely reply. I suspected the Borax was not pure borate and I am not a chemist so was lost. Looks like I need to add a bunch more.

Do I need to be concerned that the addition of acid to compensate for the Borax will further lower the alkalinity or does the addition of Borax cause the acid to work differently? I guess I could try it and find out.

Thanks for the assistance!

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Do I need to be concerned that the addition of acid to compensate for the Borax will further lower the alkalinity or does the addition of Borax cause the acid to work differently? I guess I could try it and find out.

OK, I added 10 oz. of Borax and 5 oz. muriatic acid and the alkalinity only decreased about 5 ppm so, based on this one result, I would say the acid acts on the Borax because, according to the tables, I should have lost around 50 ppm.
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Yes, the pH rise from the 20 Mule Team Borax is exactly compensated by the acid that you add, assuming you add proper amounts. If you balance the pH precisely, then there is a small rise in TA of about 5 ppm when you add 50 ppm Borates, assuming the pH is near 7.5. Don't worry about the TA. Just get the pH in balance and the TA should be fine (assuming it was near where you wanted it before you added borates).

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