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What is a Water Softener?

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A water softener is used to reduce the concentration of calcium and magnesium in hard water. Hard water is water that has been in contact with limestone or other sediments. This contact infuses the water with calcium and magnesium ions, which can cause two major kinds of problems. First, the metal ions react with soaps and detergents and hinder their ability to lather. This creates the familiar scum we know as "bathtub ring". Second, the calcium and magnesium can build up on pipes and restrict water flow. In boilers, the build up acts as a thermal insulator in the pipes, which reduces heating efficiency. It also causes the metal to overheat which can lead to major system failure in a pressurized unit.

There are two options for dealing with hard water. You can filter the water in the house through distillation, or you can use reverse osmosis to remove the calcium and magnesium in the water with a water softener. Filtering all the water in the house would be costly and inefficient, so a water softener is usually the best solution. Water softeners work by replacing the magnesium and calcium ions with sodium ions since sodium will not build up on pipes and does not react badly with soap. To replace the ions, all the water in the house runs through a bed of small plastic beads, or through a chemical matrix called a zeolite. The beads or zeolite are covered with sodium ions and as the water flows past, the sodium ions swap places with the calcium and magnesium ions. When the point is reached that the beads or zeolite contain nothing but magnesium and calcium, it is time to regenerate the beads or zeolite. To regenerate the beads or zeolite, they must be soaked in a stream of sodium. This is where the salt comes in. Salt is sodium chloride, so the water in the water softener mixes with salt to make a brine solution. The beads or zeolite are flushed with the brine solution and the sodium ions from the salt replace the magnesium and calcium ions. The remaining brine water and the magnesium and calcium ions are flushed through a drainpipe.

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