 Boric acid in equilibrium with its conjugate base the borate ion is widely used (in the concentration range 50 - 100 ppm boron equivalents) as a primary or adjunct pH buffer system in swimming pools.Boric acid is a weak acid, with p"K" (the pH at which buffering is strongest because the free acid and borate ion are in equal concentrations) of 9.24 in pure water at 25 °C.But apparent p"K" is substantially lower in swimming pool or ocean waters because of interactions with various other molecules in solution.