Moline Water Hardness & Quality Report (2026)

Moline, Illinois, the Rock Island County seat — a major Quad Cities community (the Illinois Quad Cities: Moline, Rock Island, and East Moline; the Iowa Quad Cities: Davenport and Bettendorf), the world headquarters of John Deere (John Deere and Company, one of the world's largest agricultural machinery manufacturers, founded and headquartered in Moline since 1848), and a major Upper Mississippi Valley industrial and agricultural machinery community — draws its municipal water supply from the Mississippi River via the City of Moline Water Division. Water hardness in Moline measures 137.5 mg/L — classified as moderately hard.

Moline's moderate hardness reflects the Upper Mississippi River valley's calcareous dolomite geology. The Mississippi River at Moline–Rock Island drains through the Upper Mississippi Valley: the Ordovician Galena Dolomite and Platteville Formation (highly calcareous dolostone of the Upper Mississippi region, major karst formations); the Silurian Niagara Dolomite (the major calcareous Upper Midwest dolomite); and Wisconsin Age calcareous glacial till of the Quad Cities region. The City of Moline's treatment plant reduces hardness from the Mississippi River, producing the moderate 137.5 mg/L at household taps.

At 137.5 mg/L, Moline residents encounter moderate-to-hard scale accumulation. Monthly cleaning with citric acid solution is recommended for faucet aerators and showerheads. City of Moline Water Division consistently delivers water meeting all Illinois EPA and federal EPA Safe Drinking Water Act requirements.