Water softening systems are the most common method to deal with hard water in both a residential setting. Water softeners use a process known as ion exchange, or reverse osmosis, to soften water. At a functional level, ion exchange systems remove dissolved mineral ions from hard water and replace them with sodium ions. Most water softening systems consist of two tanks. The primary tank contains special resin beads that have been coated with sodium ions. A second tank contains a salty brine solution which is used to regenerate the resin in the primary tank. As water moves through the soil it picks up mineral ions. These mineral ions become bound to the water molecule. To break this bond, ion-exchange units attract these mineral ions away from the water molecule. As the water supply enters the primary tank in the water softening system, the mineral ions are attracted to the resin beads. As they attach to the resin beads they displace the sodium ions. The sodium ions bond to the water molecules, allowing them to maintain a balanced charge. Over time the resin beads will collect so many dissolved minerals the system can’t continue removing more. Because of this, the system must occasionally be regenerated. To regenerate the system, salty water from the brine tank is used to fill the resin tank. This water displaces the mineral ions on the resin beads, replacing them once again with sodium ions. Afterward, any remaining water in the tank is flushed out of the system through a drain line. Softening water through ion exchange is a time-tested method for eliminating hard water. They are great for providing large amounts of consistent, softened water. Like most filtration systems, ion exchange systems do require a degree of maintenance. The regeneration process must occur regularly, and the owner must add salt to replenish the brine tank periodically.