Boric Acid & Borax (sodium tertaborate)

[TdiDave]

I want to add the 50ppm borates to my tub but cant find the "gentle spa". I do have strait boric acid and 20 mule Borax (sodium tertaborate).  Question is how much of each would I add to my 500 gallon tub to get 50ppm borates without any drastic changes in my TA or pH ?

[chem geek]

You can use The Pool Calculator to see that you can get 50 ppm Borates in 500 gallons by adding 16 ounces (1 pound) weight (about 17 ounces volume) of boric acid (which will only slightly lower your pH) OR by adding a combination of 24 ounces weight (about 23 ounces volume) of 20 Mule Team Borax and 12 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) (or roughly the same volume of dry acid).  Boric acid would be better to use.  If you use Borax and acid, add half the borax first, then the acid, then the rest of the borax and then the rest of the acid.