Water softeners are used in areas where the groundwater is considered hard. Hard water has more minerals, especially calcium and magnesium, than soft water. Hard water reduces the effectiveness of detergents and soaps and can clog drains and pipes.
A water softener uses softening solutions, usually containing potassium or sodium, to remove calcium and magnesium from the water. The calcium and magnesium are stored in a tank and then flushed away periodically.
Water softeners can use either potassium or sodium to soften water. The only difference between the two types is that sodium water softeners produce water with sodium, while the water produced by a potassium water softener contains potassium. The chemical process in each type is the same.
Using potassium to soften water produces water that is more environmentally friendly because plants need potassium. Potassium is also a mineral needed by the human body and the waste water can be safely used outdoors. However, sodium costs about half what potassium does.
Sodium water softeners add sodium to the diet of anyone drinking the softened water. Sodium can also damage plants and any waste water must be treated before it can be used as irrigation water. The only disadvantage to potassium water softeners is their cost.