The PoolMath calculator is handy and validates my point. For a target dose of 50 ppm "borate", PoolMath suggests adding 4582 oz of boric acid to one million lbs of water (120k gal), which comes out to 286 ppm boric acid. Boric acid (H3BO3) is 17.5% boron by weight, and 50 / 0.175 = 286.
What is...