Did you know hard water is caused by naturally dissolving minerals from sedimentary rocks, seepage, and runoff from soils? While there can be a variety of minerals in the water, hard water is predominantly calcium and magnesium. Neither of these elements are harmful to drink. In fact, they are both essential minerals and beneficial to human health. Romeoville’s water consistently meets or exceeds all EPA standards set for water quality. For a map on water hardness levels in your area, please see below.