Hard water is water that contains high concentrations of minerals. The ions that are of concern are calcium (Ca2+) and magnesium (Mg2+). These minerals are naturally occurring and enter the water as calcium carbonate (limestone) or calcium sulfate. The source of magnesium is called dolomite and has the following formula: CaMg(CO3)2.

You can easily determine if you have hard water in your home by doing a simple test called lather (or froth) test. Soap usually lathers (or creates foam) with soft water, which is difficult to do with hard water, hence the terminology "hard water".

Water hardness can also be determined using analytical methods such as wet titration or using analytical instruments.

In order to have an idea of the different grades of water hardness, the following is a rough estimate of level hardness compared to mineral concentrations:

. Soft: 0 - 20 mg/L as calcium
. Moderately soft: 20 - 40 mg/L as calcium
. Slightly hard: 40 - 60 mg/L as calcium
. Moderately hard: 60 - 80 mg/L as calcium
. Hard: 80 - 120 mg/L as calcium
. Very Hard >120 mg/L as calcium

Soft water is essentially free of dissolved calcium or magnesium

Since calcium and magnesium are not present in soft water, no adverse reaction with soaps and detergents occurs. The result is the virtual elimination of soap scum and the corresponding reduction in time spent cleaning. Hair and skin can "breathe" more readily. And the School of Consumer & Family Sciences at Purdue University recently conducted a study which proved that the life of clothing and household textiles was prolonged up to 15 percent when they were washed in conditioned water.

Soap usage can be dramatically reduced with soft water. Since the water is already soft, the cleaning agents have no hardness minerals to react with and overcome, lather more readily and work more effectively. Since less is needed, households can experience considerable savings on laundry detergent, dishwashing detergent, bath soap, hand soap, shampoo and many other cleaning products.

Since soft water contains no scale forming minerals, it leaves the inside of plumbing and water using appliances free of solidified rock. Appliances operate more efficiently and last longer when using soft water. Leading appliance manufacturers including Maytag have recognized the problems that hard water causes and recommend the use of home water conditioners to help their own products operate more efficiently.

How Water Is Softened

The most common method used for softening water is ion exchange, where the dissolved calcium and magnesium ions are exchanged for sodium or potassium (commonly referred to as regenerant) ions. Sodium and potassium do not cause the problems that are associated with calcium and magnesium. The process is the basis for most water softening equipment on the market today.

Water enters a water softener where it comes in contact with a bed of tiny beads that hold sodium chloride or potassium chloride ions. Since the beads are chemically more attracted to calcium and magnesium ions, ion exchange occurs. The calcium and magnesium ions "stick" to the surface of the beads, dislodging the sodium or potassium. After the beads are completely exhausted (i.e. covered with calcium and magnesium), a solution is introduced to the system to wash away the calcium and magnesium, and replace the sodium or potassium (a process known as regeneration). After the extra solution is rinsed from the resin bed, the entire ion exchange cycle begins again.