I'm sure the chemists will chime in here, but I'm guessing that the Borax in this product is not for pH control--rather, it is to add the borates to the water. A borate level of around 50 ppm has been known to inhibit algae growth and give the water a crisper look and feel. However, since it also raises pH, the acid is added to counter that pH rise. You can buy a lot of Borax and acid for less than $16.....
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Janet