Grayslake Water Hardness & Quality Report (2026)

Grayslake, Illinois, in Lake County — a Lake County village in the northern Illinois suburban corridor, home of the Lake County Fairgrounds and a growing north suburban Chicago residential community on the Chain O'Lakes waterway system — receives its municipal water from Illinois American Water or the Grayslake Water Division, which draws from Lake Michigan through the Lake County regional water supply system (purchased from North Chicago or Waukegan's Lake Michigan intake) for the northern Lake County distribution zone.

The moderately hard 118 mg/L hardness and TDS of 191.1 mg/L reflect Lake Michigan's characteristic chemistry at the Lake County northern Illinois distribution level — consistent with the Lake Michigan supply throughout Cook and Lake Counties. Lake Michigan draws from the Canadian Shield (soft Precambrian granite and gneiss through northern Michigan and Wisconsin tributaries) but also from the Silurian Niagara Dolomite escarpment of the Door Peninsula and eastern Wisconsin, contributing moderate carbonate hardness. The northern Lake County distribution system delivers Lake Michigan water that's slightly moderated by treatment and distribution but maintains the characteristic Lake Michigan moderate-hardness profile.

At 118 mg/L, Grayslake's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 4.3 ppt is favorable for the Chicago metro — Grayslake's suburban residential character, the northern Lake County corridor's limited direct PFAS point sources, and Lake Michigan's large dilution capacity produce a modest PFAS background for the northern Illinois suburban zone.