South Chicago Water Hardness & Quality Report (2026)

The City of Chicago Department of Water Management supplies water to South Chicago, Illinois, as part of the broader Chicago metropolitan area. The primary source is Lake Michigan, drawn from intake cribs located offshore in the lake. Water is treated at the Jardine Water Purification Plant (formerly South District Filtering Station) and the Zimmerman Water Filtration Plant, serving the South Side including South Chicago. The service area covers Cook County, delivering water to over 5 million residents in Chicago and 100 suburbs through approximately 6,000 miles of pipes.

Lake Michigan forms the core watershed as part of the binational Great Lakes system spanning multiple states. The lake basin overlies Paleozoic sedimentary rocks — notably Silurian and Devonian dolomites and limestones — that weather to release calcium and magnesium ions. Pleistocene glacial till further influences sediment load. This geology imparts a hard character to the supply as surface water contacts carbonate-rich substrates; dilution from high rainfall moderates extreme hardness compared to inland groundwater sources.

Hard water promotes scale buildup from mineral deposits, primarily affecting water heaters, dishwashers, washing machines, and coffee makers by reducing efficiency and lifespan. Soap scum on fixtures, drier skin and hair, and spotted dishes are common. Regular maintenance — deliming appliances, vinegar rinses, and drain screen installation — helps mitigate effects; a water softener is recommended for households with noticeable scaling. Chicago water maintains a pH of 7.5–8.5 due to lime softening; the utility complies with EPA lead and copper rules through corrosion control and pipe replacement programs. No significant PFAS exceedances reported in recent CCRs; treatment involves screening, coagulation with lime and alum, sedimentation, dual-media filtration, and chloramination.