How do you remove permanent hardness of water?

The permanent hardness of water is caused by dissolved doubly or triply charged metal cations, which must be removed to remove the permanent hardness. Distillation is a traditional method for removing these and all other ions, but a more economical solution under most circumstances is contacting the water with an ion exchange medium that can replace the doubly or triply charged cations with singly charged cations such as those of sodium and/or potassium. The reason this works is that most doubly or triply charged cations form precipitates with the anionic portion of soaps or anionic detergents, but singly charged cations form more soluble salts that do not precipitate.