Common Water Quality Problems > Hardness


The term “hardness” originally referred to the soap-consuming power of water.  Today hardness or “hard water” as it is frequently called, refers to a common characteristic of ground water in most areas of North America.

Ground water as it moves through limestone bedrock or carbonate-rich overburden dissolves calcium and magnesium compounds which in turn increase the hardness of water. The concentration of calcium and magnesium salts in water is usually expressed as grains/gallon, PPM, or mg/L as COCO3.

      Degrees of Water Hardness

SOFT     Less Than   1.0 Grain/Gallon Less than      17.0   Mg/Liter
SLIGHTLY HARD 1.0 To   3.5 Grain/Gallon 17.1 To   60.0   Mg/Liter
MODERATELY HARD 3.5 To   7.0 Grain/Gallon 60.0 To 120.0   Mg/Liter
HARD  7.0 To 10.5 Grain/Gallon 120.0 To 180.0   Mg/Liter
VERY HARD 10.5 & Over Grain/Gallon  180.0 & Over      Mg/Liter

At 10 GPG (grains per gallon) of hardness, the average household can use up to four times the amount of soap or detergents as would be required for soft water.

At 20 GPG (grains per gallon) of hardness the scale build-up can be so severe that hot water heaters may have to be replaced as often as every three years, and the service life of appliances can be cut in half.

Surveys show that at 25 gpg, hard water costs the average family over US $ 75 per month. At 50 gpg, the cost soars to over US $ 125 per month.



 Water softeners