The usual way to soften water, ion exchange involves calcium and magnesium ions being switched for sodium or potassium (regenerate) ions, which don't cause the problems the other two minerals are known for. Inside the softener, an ion exchange material - such as a bed of small, plastic resin beads or zeolite - is saturated with sodium or potassium chloride. The material draws in calcium and magnesium, which displace the sodium or potassium into the water. When the material is completely covered through exchange, a solution washes away the removed minerals and replaces the regenerate ions before the tank is rinsed with fresh water. This process is known as regeneration.
Ion exchange water softeners cost from $500 to over $1,000 depending on grain capacity (number of grains that can be removed before discharging is necessary), and installation is often extra. Operating costs can vary depending on how the water softener operates, be it through electricity or through water. Yearly costs of water softener salts can be upward of $50, depending on the type. Anyone purchasing a water softener in the United States should be aware that some states are introducing legislation to ban water softeners, so make sure you'll be able to use it before you buy it. If you do buy an ion exchange water softener, look for one that regulates itself and has a high enough capacity to last several days before regenerating - it will save you money and reduce the amount of brine (salt) water being released as waste.
Ion exchange water softeners have varying levels of automation: