Water softening refers to a method of filtration by which “hard” water is made soft.
Hard water is any water containing dissolved hardness minerals above 1 Grain per Gallon or 17.1 Parts per Million. The total dissolved hardness minerals are most often in the form of calcium, magnesium, and certain other metals.
The most common way to soften water involves an ion-exchange process to replace hardness minerals in the water with another substance, such as sodium. Typically, water softeners are filled with beads of resin. Each bead of resin contains a slight electric charge which binds sodium ions to its surface. As hard water pours into the softener, it flows through the resin beads. The hardness minerals in the water have a stronger attraction to the beads than the sodium. Therefore, they attach themselves to the beads and displace the sodium ions. This is why the process is known as an ion exchange.
Eventually, the resin is coated in hardness ions and can no longer effectively soften the water. At this point, the softener will begin its “regeneration” cycle to cleanse the resin. In regeneration, a brine solution featuring an extreme concentration of sodium ions is delivered from the brine tank to the softener. The salty brine reverses the ion-exchange process to scrub the hardness from the resin before being flushed away, leaving the softener once again ready to remove calcium and magnesium ions from hard water.
Mechanical water softeners using ion-exchange are the best performing, longest lasting softeners available. Softening options such as chemical treatment and magnetic water softening range from significantly less effective to downright useless. Recent advances in technology have greatly reduced the amount of electricity and sodium used by modern water softeners, and a high quality softener should be an essential part of any modern home.