Water Hardness

Hardness is caused by compounds of calcium and 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 the City of Abilene is considered "hard" to "very hard." The table below is provided as a reference.


Grains per Gallon Milligrams per Liter or Parts per MillionClassification
Less than 1.0Less than 17.1Soft
1.0 to 3.517.1 to 60Slightly Hard
3.5 to 7.060 to 120Moderately Hard
7.0 to 10.5120 to 180Hard
Over 10.5Over 180Very Hard

 City of Abilene Water Hardness

Grains per Gallon Milligrams per Liter or Parts per MillionClassification
8.0 to 12.0136.9 to 205.4Hard to Very Hard

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). On average, the calcium levels found in the water delivered by the City of Abilene could contribute between 14% to 21% of the Recommended Daily Allowance of calcium for an adult.

 Hardness does not pose a health risk to the public and is not regulated by state or federal agencies. But hard water can be a nuisance due to the mineral buildup on plumbing fixtures and poor soap and detergent performance. It often causes aesthetic problems, such as an alkali taste to the water that makes coffee taste bitter; build-up of scale on pipes and fixtures than can lead to lower water pressure; build-up of deposits on dishes, utensils and laundry basins; difficulty in getting soap and detergent to foam; and lowered efficiency of electric water heaters.

Water customers may treat hard water by adding a water softener to laundry and the dishwasher or by installing a water softener system to treat all of your household water. The City does not provide a recommendation for the public with respect to installing water softener systems; the decision to soften water is a personal one and should be done following one's own analysis and research.