Water hardness refers to the mineral content of water, commonly calcium and magnesium. Typically, our water is "moderately hard" to "hard" (5 - 10 grains per gallon, or 84 - 170 mg/l). Water hardness is naturally occurring and depends on the amount of minerals in our source waters: the Potomac River and Occoquan Reservoir. It may vary depending on location and the amount of rainfall.
Sometimes water hardness can cause a build-up of white residue on appliances or dishware. This white residue found is usually the result of the dissolved minerals found in water, such as calcium and magnesium. Mineral particles may also be visible in ice cubes made with tap water. These minerals are not a risk to human health but can build up on surfaces over time. Commercial products are available to remove white residue caused by minerals.