A water softener does not put salt into the water.
It merely exchanges calcium ions in the water for sodium or potassium ions. The amount of sodium or potassium coming through in soft tap water is extremely low. For example, in 10 grain hard water, the amount of sodium in an 8 ounce glass of soft water is typically equivalent to the sodium in one slice of white bread. Soft water, by dietary standards, would be considered a “low sodium” beverage. Consumers may use potassium as a regenerant if they prefer not to clean out the system with sodium. Be sure to check on the efficiency of the water softener before using potassium as it is higher priced and 25% less efficient than sodium as a regenerant.