Des Plaines Water Hardness & Quality Report (2026)

The City of Des Plaines Water Department serves approximately 60,000 residents in Cook County, Illinois. Water is purchased from the City of Chicago, which draws from Lake Michigan via two major intake cribs in the lake. Primary treatment is carried out at Chicago's Jardine and South Water Purification Plants, with secondary handling at Des Plaines pumping stations and storage tanks distributed through approximately 200 miles of mains. The supply undergoes filtration, disinfection, and fluoridation per the Chicago process, and the 2024 Consumer Confidence Report confirms compliance with lead and copper rules.

The source water originates from Lake Michigan, part of the Great Lakes watershed draining into the St. Lawrence River. Underlying regional geology features glacial till overlying Silurian dolomite and limestone bedrock belonging to the Niagaran Series, a carbonate-rich Paleozoic formation prevalent in the Chicago region. While Lake Michigan water begins relatively soft, conveyance through mineral-bearing infrastructure and interaction with regional limestone aquifers adds calcium and magnesium during treatment and distribution, resulting in a moderately hard supply prone to mineral accumulation.

Moderately hard water promotes scale buildup in pipes, heaters, and fixtures, reducing efficiency in water heaters, dishwashers, and washing machines. Soap lathering decreases, leaving residue on skin, hair, and laundry. Regular deliming of appliances and flushing systems is recommended; a water softener is advised to mitigate these effects and extend equipment life. Seven contaminants exceed health guidelines per EWG analysis, including bromodichloromethane; the 2024 Consumer Confidence Report confirms regulatory compliance, and pH is typically neutral to slightly alkaline from lake sourcing and treatment.