Water Hardness Information
The Environmental Protection Agency (EPA) establishes standards for drinking water which fall into two categories — Primary Standards and Secondary Standards. Primary Standards are based on health considerations and Secondary Standards are based on aesthetics such as taste, odor, color, or corrosivity. There is no Primary or Secondary standard for water hardness. In fact, the National Research Council (National Academy of Sciences) states that hard drinking water generally contributes a small amount toward total calcium and magnesium human dietary needs (National Research Council, Drinking Water and Health, Volume 3, National Academy Press, Washington, D.C., 1980).
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). The table below is provided as a reference.
As of December 22, 2015 the Occoquan Forest Water System has been connected to the Prince William Water-East system, which is supplied by the Frederick P. Griffith Jr. Water Treatment Plant operated by Fairfax Water.
Grains Per Gallon | Milligrams Per Liter (mg/L) | Classification |
Less than 1.0 | Less than 17.1 | Soft |
1.0-3.5 | 17.1-60 | Slightly Hard |
3.5-7.0 | 60-120 | Moderately Hard |
7.0-10.5 | 120-180 | Hard |
Over 10.5 | Over 180 | Very Hard |
East and West Water Systems
Grains Per Gallon | Milligrams Per Liter (mg/L) | Classification |
3.5-7.0 | 60-120 | Moderately Hard |
Bull Run Mountain and Evergreen Water System
Grains Per Gallon | Milligrams Per Liter (mg/L) | Classification |
7.0-10.5 | 120-180 | Hard |
Hoadly Manor System
Grains Per Gallon | Milligrams Per Liter (mg/L) | Classification |
7.0-10.5 | 120-180 | Hard |