A paper contributed to and selected by the JOURNAL by Terence J. McGhee (Active Member, AWWA), assoc. prof., Dept. Civ. Engrg., Tulane Univ., New Orleans, La. __Here is a textbook type approach to water-softening calculations that should produce a better understanding of what transpires during the treatment process. Although actual operating conditions usually will require dosage modifica tions through empiricism, the technique is valuable because it readily provides first order approximations.