Many industrial and domestic water users are concerned about thehardness of their water. Hard water requires more soap and synthetic detergents for home laundry and washing ,and contributes to scaling in boilers and industrial equipment. Hardness is caused by compounds of calciumand magnesium, and by a variety of other metals. Water is an excellent solvent and readily dissolves minerals it comes in contact with. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution.

Calcium and magnesium dissolved in water are the two most common minerals that make water "hard."

The hardness of water is referred to by three types of measurements: grains per gallon, milligrams per liter (mg/L), or parts per million (ppm). Typically, the water produced by Fairfax Water is considered "moderately hard" to "hard." The table below is provided as a reference.