Water described as "hard" means it is high in dissolved minerals, specifically calcium and magnesium. Hard water is not a health risk, but a nuisance because of its tendency to cause mineral buildup in water pipe and heating systems, and its poor soap and/or detergent performance when compared with soft water.
Water is a good solvent and picks up impurities easily. As water moves through soil and rock, it dissolves minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases.
When you consider that ¼ inch of scale in your water heating element will cause you to use 40% more energy to heat up water, lime scale can have a significant impact in your wallet as well as environmental consequences.
Water Conditioners or Water Softeners?
Traditionally the water treatment market had one main solution to hard water: salt based water softeners. However, in recent years alternative treatments have become increasingly popular, the most interesting of which is electronic water conditioning.
Water Softeners work by ion exchange, so sodium replaces the calcium and/or magnesium in the water. Electronic Water Conditioners on the other hand create an electric field around your pipework which alters the ions in the water so that they loose their ability to cause scale. In tackling hard water, both methods will reduce limescale. Electronic Water Conditioners are significantly less expensive to start with and they have negligible running costs. Water Softeners cost a lot more and have the added downside that they require large amounts of salt to be purchased and added, they use additional water for regenerating and then they discharge salt into the environment causing environmental problems that have caused many communities to make the use of salt based softeners illegal. Small Wonder and Scalewatcher electronic hard water treatment systems are approved alternatives to salt based water softeners.
85% of the U.S has hard water:
To read an interesting interpretation of above map and real water hardness in the USA Click Here