Lower West Side Water Hardness & Quality Report (2026)

The Chicago Department of Water Management supplies water to Lower West Side, Chicago, Illinois, serving Cook County and surrounding west side neighborhoods with over 2.1 million residents. Water is sourced exclusively from Lake Michigan via two major intake cribs, treated at the Jardine Water Purification Plant and the Zimmerman Water Filtration Plant on the lakefront. No local groundwater is used; treatment involves screening, chemical coagulation with alum, sedimentation, dual-media filtration, chlorination, and fluoride addition.

The watershed is the Lake Michigan basin within the Great Lakes system, fed by precipitation and upstream rivers with glacial influences from the Pleistocene epoch. Underlying geology features Paleozoic carbonate rocks including the dolomite-rich Racine and Waukegan Formations (Silurian), which dissolve to impart minerals during raw water withdrawal. This yields a characteristically hard supply due to natural mineral leaching from limestone and dolomite, moderated by the lake's large volume compared to groundwater sources but still elevated in dissolved calcium and magnesium.

Hard water causes scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. White deposits on fixtures and soap scum are common, increasing detergent use. Regular descaling of appliances and fixtures is recommended; a water softener is advised for very hard conditions to protect plumbing and improve cleaning. Chicago's water meets EPA standards with pH typically 7.5–8.5; lead/copper rule compliance is strong with no actionable exceedances. No PFAS violations have been reported in recent CCRs, and occasional taste or odor issues from algae are managed with powdered carbon.