To the Editor.—
The letter by McGarvey (227:1258, 1974) concerning the sodium content of water-softened water is both incorrect and misleading. The sodium chloride used to regenerate the ion-exchange resins of home water-softeners does just that; it exchanges sodium ions for the calcium and magnesium ions removed from the water. These calcium and magnesium ions are then removed in the backwash cycle of the regeneration process as the chloride salt. Thus, all the chloride ions are removed. As fresh water then goes through the regenerated resin bed, the hardness elements, calcium and magnesium, replace the sodium on the resin, and the sodium goes into the drinking water as the salt of the anion to which the calcium and magnesium ions were formerly bound. This is usually a sulfate, carbonate, or bicarbonate. The only chloride ions in the water are the chloride ions that were in the water before it was softened.