Mokena Water Hardness & Quality Report (2026)

Mokena, Illinois, in Will County — a Will County village in the southwest Chicago suburbs adjacent to New Lenox and Frankfort, part of the rapidly growing Will County suburban corridor on the I-80 corridor — receives its municipal water from the Village of Mokena Water Department or Illinois American Water, which draws from the Des Plaines River or the Kankakee River through the Will County regional water supply system.

The moderately hard 137.5 mg/L hardness and TDS of 239.9 mg/L reflect the Des Plaines-Kankakee River watershed's Illinois carbonate till plain character. The Des Plaines River and Kankakee River drain the Illinois Till Plain — the flat glaciated terrain of northeastern Illinois, underlain by Silurian Niagara Dolomite, Devonian limestone, and the Cambrian carbonate platform. The Pleistocene glacial till in Will County contains abundant calcareous carbonate clasts from the Great Lakes carbonate terrain, contributing calcium and bicarbonate to the regional surface water and shallow groundwater system.

At 137.5 mg/L, Mokena'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 4.9 ppt warrants a certified drinking water filter — the Joliet Arsenal (former US Army ammunition depot in the Will County-Kankakee corridor), the Channahon industrial corridor, and the southwest Chicago suburban manufacturing belt contribute to the Will County PFAS readings.