Why do water softeners have to add salt to the water?
The first thing to remember, is any salt in softened water is a by product of the softening process. The softener works by passing the hard water through resin beads, which attract the hard mineral ions to them. This process is called “ion exchange” It takes place with the hard mineral ions (typically calcium and/or magnesium) trading places with the soft sodium/potassium ions. After a period of use the sodium ions are depleted being replaced by calcium and magnesium. The resin then needs to be regenerated with the sodium ions so the resin will again be able to exchange the hard for the soft.
