Skip to main content


Water Hardness

Hard water is high in dissolved minerals, largely calcium and magnesium. Water hardness is measured by the amount of dissolved calcium and magnesium in the water. General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft; 61 to 120 mg/L as moderately hard; 121 to 180 mg/L as hard; and more than 180 mg/L as very hard.

Very hard water is prevalent in the east-central and western United States, reflecting the distribution of carbonate aquifers and aquifers with relatively high concentrations of dissolved solids.  The Bucks/Montgomery County area of Southeast Pennsylvania is an area that has very hard water.

Hard water is not a health concern, but it can be a nuisance. Hard water can cause mineral buildup in plumbing, fixtures, and water heaters, and poor performance of soaps and detergents. One of the most common causes of cloudy dishes and glassware is hard water. 

But hard water can have some benefits, too. Humans need minerals to stay healthy, and the World Health Organization (WHO) states that drinking-water may be a contributor of calcium and magnesium in the diet and could be important for those who are marginal for calcium and magnesium intake.

Many industrial and domestic water users are concerned about the hardness of their water. When hard water is heated, such as in a home water heater, solid deposits of calcium carbonate can form. This scale can reduce the life of equipment, raise the costs of heating the water, lower the efficiency of electric water heaters, and clog pipes. Mineral buildup is also likely to occur in home coffee makers too, which is why some people occasionally run vinegar (an acid) through the pot. The acidity of vinegar helps to dissolve mineral particles by making them charged. These newly charged particles become attracted to the positive and negative charges in water and can be washed away easily.

Should you choose to treat your water by installing a home water softener, the installation instructions may ask you to input the hardness of the incoming water supply.  Horsham uses a number of water sources, which are all considered “very hard”, ranging from ~200 to ~350 mg/l as calcium carbonate (Many water softeners measure hardness in grains per gallon or gpgs. The conversion is 1 gpg = 17.1 mg/l of calcium carbonate). Using an average of approximately 275 mg/l as calcium carbonate or 16 gpg should be sufficient.

water_hardness.pdf (139.16 KB)