Rochester Water Hardness & Quality Report (2026)

Rochester Public Utilities (RPU) serves Rochester, Minnesota, drawing water from 31 deep groundwater wells distributed throughout the city, most 24 inches in diameter and extending 400–1,000 feet in depth. Water is pumped directly from the wells into the distribution system with no surface reservoir. Treatment chemicals — chlorine for bacteria control, hydrofluosilicic acid for fluoridation, and liquid blended polyphosphate for corrosion protection — are added at each well house site serving the city.

Rochester's water originates from water-bearing rock layers called aquifers. The primary source is the Jordan Aquifer, a deep sedimentary unit underlying southeastern Minnesota. Additional water is drawn from multi-formation wells including the Prairie du Chien-Jordan, Prairie du Chien-Wonewoc, Jordan-Wonewoc, and Prairie du Chien-Mt. Simon aquifers. The sub-rock beneath Rochester is predominantly limestone, a carbonate formation that readily dissolves, releasing calcium and magnesium ions into the groundwater and creating a very hard water supply.

Very hard water results in increased scale buildup in pipes, water heaters, and appliances, requiring more soap and detergent for cleaning. Households may experience reduced efficiency in dishwashers, washing machines, and water heaters due to mineral accumulation. RPU recommends that those installing ion exchange water softeners maintain a separate, unsoftened supply for cooking and drinking, as softened water replaces calcium and magnesium with sodium. Regular descaling of appliances and water heater maintenance are advisable. The water is treated with chlorine for disinfection, fluoride for dental health, and polyphosphate for corrosion control and iron stabilization; bromodichloromethane has been detected above health guidelines in the supply.