Why are acids dangerous? We use the pH scale to give one a relative scale of physical hazard to that of water, or H2O. The pH scale has a range of 0 to 14, with water having a pH=7, or neutral. A pH of 1 indicates an acid (i.e. hydrochloric acid), whereas a pH of 14 (i.e. drain cleaner, lye) indicates an alkaline (base).