Quincy Water Hardness & Quality Report (2026)

Quincy, Illinois, the Adams County seat on the Mississippi River — a major west-central Illinois Mississippi River city, a historic Abraham Lincoln–Stephen Douglas debate site (the sixth Lincoln–Douglas debate, 1858), a major Illinois river port and agricultural shipping community, and a significant German-American and African-American heritage city (Quincy was a major stop on the Underground Railroad, with over 100 enslaved people helped to freedom through the Quincy anti-slavery networks) — draws its municipal water supply from the Mississippi River via the City of Quincy Water Division. Water hardness in Quincy measures 182 mg/L — classified as hard.

Quincy's hard supply reflects the Upper Mississippi River valley's calcareous dolomite geology. The Mississippi River at Quincy–Adams County drains through: the Ordovician Galena Dolomite and Platteville Formation (highly calcareous dolostone of the Upper Mississippi region — the same calcareous formations that produced the Galena lead mines of northwest Illinois and southwest Wisconsin); the Devonian Wapsipinicon Formation (calcareous dolomite of the Iowa–Illinois Devonian sequence); and Wisconsin Age calcareous glacial till of the Adams County Illinois prairie zone. The City of Quincy's treatment plant produces the hard 182 mg/L.

At 182 mg/L, Quincy residents face regular hard water challenges. Monthly descaling with citric acid solution is standard maintenance. City of Quincy Water Division consistently delivers water meeting all Illinois EPA and federal EPA Safe Drinking Water Act requirements.