Water hardness is determined by the concentration of dissolved minerals, specifically calcium and magnesium ions, present in the water supply. For residents of the Chicagoland area, the water is generally classified as moderately hard to hard. This mineral content is not a health concern, but it does influence the daily function and maintenance of household plumbing and appliances.
Defining Water Hardness in Chicago
Water hardness is precisely measured using two common units: parts per million (PPM) or grains per gallon (GPG). One GPG is equivalent to 17.1 PPM, and this metric is used to categorize water on a standardized scale. Water supplies that fall within the range of 7.1 to 10.5 GPG are officially categorized as “hard.” Chicago’s water typically averages between 7.6 and 8.8 GPG, which places it firmly within the hard water classification.
The Source of Chicago’s Water Minerals
Chicago draws nearly all of its drinking water from Lake Michigan. The origin of the water’s hardness is directly linked to the regional geology of the Great Lakes basin. As the water travels, it flows over and through vast underground deposits of sedimentary rock, primarily limestone. Limestone is rich in calcium carbonate and magnesium carbonate, which readily dissolve into the water supply. The Chicago Water Department provides extensive treatment, including filtration and disinfection, to ensure the water is safe to drink, but standard municipal processes do not remove the bulk of these naturally occurring hardness minerals.
Practical Effects on the Home and Appliances
The most noticeable effect of hard water is the formation of limescale, a crusty white or yellowish deposit composed mainly of calcium carbonate. This mineral buildup adheres to surfaces that regularly come into contact with water, such as faucets, showerheads, and porcelain fixtures. Within the home’s plumbing system, limescale accumulation on the heating elements of water heaters dramatically reduces their energy efficiency. The deposits act as an insulator, forcing the appliance to work harder and increasing energy consumption. Hard water also interferes with cleaning, as dissolved calcium and magnesium ions react with soap and detergent, inhibiting lathering and creating soap scum that clings to surfaces and leaves spots on dishes.
Managing Hard Water
For homeowners seeking a comprehensive solution, a whole-house water softening system is the most effective method for dealing with hard water. These systems use ion exchange to remove calcium and magnesium ions, swapping them with sodium or potassium ions that do not cause scale buildup or interfere with soap. The resulting softened water protects the entire plumbing system and all water-using appliances from further mineral damage. Point-of-use filters, such as those found in pitchers or mounted on faucets, are primarily designed to improve taste and remove certain contaminants, but they are not effective at reducing water hardness. For simple maintenance, residents can use descaling agents like white distilled vinegar or citric acid on fixtures or run through appliances to dissolve existing limescale.