Minneapolis Water Hardness & Quality Report (2026)

Minneapolis's water is supplied by Minneapolis Water Works, drawing from the Mississippi River at the St. Anthony Falls Water Treatment Plant — located at St. Anthony Falls, the only natural waterfall on the entire Mississippi River and the city's original industrial power source. This facility processes all of Minneapolis's drinking water supply, treating Mississippi River water that originates in the lake-rich headwaters of northern Minnesota before flowing south through the Twin Cities metro area. Minneapolis Water Works also operates the Columbia Heights Water Treatment Plant north of the city. Minneapolis is one of the largest US cities to rely on a single river intake, and significant investment in treatment and watershed protection has been made to maintain supply reliability.

Minneapolis's moderate hardness of 202 mg/L reflects the carbonate geology of the upper Mississippi River watershed. The Mississippi above Minneapolis flows through central Minnesota's lake country, draining terrain underlain by Precambrian granite and gneiss (soft) but also traversing exposures of Ordovician Prairie du Chien Group dolostone, Oneota Formation, and St. Peter Sandstone — carbonate and calcareous sedimentary formations that contribute meaningful mineral loading to the river. Tributary inputs from the Minnesota River and other central Minnesota streams cross Cretaceous chalky shale and Quaternary glacial carbonate till, adding further calcium and magnesium bicarbonate to the blended Mississippi flow at St. Anthony Falls.

Minneapolis residents experience moderately hard water effects: scale deposits form on faucets and inside appliances over months, soap and detergent performance is slightly reduced, and dishwashers produce some glassware spotting without rinse-aid. The Mississippi source creates seasonal hardness variation — spring snowmelt periods tend toward slightly softer readings while late-summer low-flow periods produce harder tap water. Descaling kettles and coffee makers every 2–3 months is practical, and rinse-aid in dishwashers handles glassware filming. A carbon-block filter further improves taste by reducing any residual treatment chemical presence.