What is Hard Water?

As water passes through soil and rock, it dissolves and retains tiny amounts of minerals 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 calcium and magnesium concentrations increase.

Hard water is not a health risk; it simply contains a higher concentration of natural minerals. However, it is a nuisance to equipment and taps, as it will more likely lead to scale buildup and generate premature damages.

The Water Quality Association has developed a water hardness table (shown below).

	Water Hardness Table     Grain per gallon PPM   Soft Less than 1 Less than 17.1   Slightly Hard 1 to 3.5 17.1 to 60   Moderately Hard 3.5 to 7 60 to 120   Hard 7 to 10.5 120 to 180   Very Hard 10.5 and up 180 and up
Source: Water Quality Association

Hard water is a common natural phenomenon. For example, over half of the United States territory is supplied with water that is qualified as hard to very hard (see map).

	Click on the map to see a close-up

How Does Scale Form?

As mentioned above, the harder the water, the greater the formation of scale.

Scale is the result of the crystallization of minerals found in water. This crystallization process is even more intense in warm water.

As water temperature rises, water minerals such as calcium and magnesium tend to crystallize, clump together, and form deposits on the inside walls of pipes or any other surface they touch.