Lisle Water Hardness & Quality Report (2026)

Lisle, Illinois, in DuPage County along the East Branch DuPage River — home to the world-renowned Morton Arboretum and Illinois Benedictine University, a model DuPage County suburban community at the junction of I-88 (East-West Tollway) and I-55 — receives its municipal water from the Village of Lisle Public Works Water Division, which purchases treated water from the DuPage Water Commission (DWC). The DWC draws from Lake Michigan via the Chicago Department of Water Management regional treatment system and delivers treated water to suburban DuPage County communities.

The moderately hard 151 mg/L hardness and TDS of 276.4 mg/L reflect the Lake Michigan-supplied DuPage County water character. Lake Michigan receives its substantial carbonate hardness from the Great Lakes basin tributaries draining the Silurian Niagara Dolomite reefs of Michigan, Wisconsin, and northern Illinois, as well as Devonian carbonate inputs from the Michigan Basin. The DWC treatment process removes taste, color, and biological contaminants but does not reduce the naturally occurring carbonate hardness — Lisle's water supply matches the general DuPage Water Commission finished water profile, consistent with the Lake Michigan-sourced supply throughout the DuPage suburban corridor.

At 151 mg/L, Lisle residents experience moderately hard water consistent with DuPage County's Lake Michigan supply. Scale builds in kettles and coffee machines over months, dishwashers benefit from rinse aid, and bathroom fixtures develop calcium deposits. Quarterly descaling of heating appliances is the standard schedule for DuPage County households. The PFAS level of 5.4 ppt warrants a certified drinking water filter — the Lake Michigan supply serves the heavily industrialized Chicago metro region, and the DuPage corridor's historical industrial land use and Superfund sites contribute PFAS to the regional supply baseline.