Champaign Water Hardness & Quality Report (2026)

Champaign, Illinois — home of the University of Illinois Urbana-Champaign — in Champaign County, draws its municipal water supply from the Mahomet Aquifer via the City of Champaign Public Works Water Division. The Mahomet Aquifer is a Pleistocene buried valley aquifer — a preglacial river valley (the ancestral Mahomet River valley) filled with clean outwash sand and gravel during the Pleistocene glaciations — one of the most important aquifer systems in the Illinois Basin. Water hardness in Champaign measures 149.5 mg/L — classified as hard.

Champaign's hard supply reflects the Mahomet Aquifer's mineralisation in the Champaign County zone. The Mahomet Aquifer sand and gravel fill draws on recharge from the surrounding Illinois glacial till — which contains calcareous carbonate-rich till derived from the Pennsylvanian limestone and shale cyclothems of the Illinois Basin (Salem Limestone, Warsaw Formation, Keokuk Limestone) that underlie the glacial overburden. The confined character of the aquifer in areas allows longer groundwater–sediment contact time, with carbonate equilibration against the calcareous outwash and till. The high-quality, prolific Mahomet Aquifer supplies municipalities across central Illinois, but consistently delivers hard supply in Champaign County.

At 149.5 mg/L, Champaign residents face regular hard water challenges. Scale deposits form on faucet aerators, showerheads, and appliances within weeks — monthly descaling with citric acid solution is standard maintenance. Dishwashers require rinse-aid, and water heaters benefit from annual inspection. City of Champaign Public Works and UIUC campus water consistently deliver water meeting all Illinois EPA and federal EPA Safe Drinking Water Act requirements.