Frequently used to provide softened water for heavy commercial, industrial, and municipal applications. Water containing calcium and magnesium (i.e. hardness) is not suitable for many uses because of its tendency to form mineral scale, soap scum, and chemical sludges. Water softeners use ion exchange resin to exchange the calcium, magnesium, and other scale forming minerals for sodium. Since sodium does not form hard mineral scale the process is referred to as water softening.