Elk River Water Hardness & Quality Report (2026)

Elk River, Minnesota, in Sherburne County on the Mississippi River at the mouth of the Rum River — a growing outer-ring Twin Cities suburb and the seat of Sherburne County — receives its municipal water from the City of Elk River Public Works, drawing from the Mississippi River through a surface water intake at the Elk River reach. The Rum River, originating in Mille Lacs Lake, contributes flow from the central Minnesota lake district at this confluence before the combined flow continues south toward the Twin Cities metro.

The very hard 262 mg/L hardness and high TDS of 666.9 mg/L reflect the Mississippi River's carbonate basin character in central Sherburne County. The Mississippi in the Twin Cities metro region drains the Ordovician Galena Group and Prairie du Chien Group dolomite, Jordan Sandstone, and Oneota Dolomite — Paleozoic carbonate and calcareous formations of the Minneapolis–St. Paul basin — contributing substantial calcium and magnesium bicarbonate from river baseflow. The Rum River addition brings water from the Precambrian Canadian Shield fringe watershed around Mille Lacs Lake, somewhat softer, but the mainstream Mississippi carbonate burden dominates the blended supply at the Elk River intake.

At 262 mg/L, Elk River households face very hard water affecting all home systems. Scale builds rapidly in kettles and coffee machines within weeks, dishwashers need water softener treatment to produce clean glassware, and bathroom surfaces develop calcium deposits requiring regular acidic cleaning. Descaling appliances every four to six weeks is the practical schedule for Elk River households. A whole-house water softener is strongly recommended for this Sherburne County community. The PFAS level of 7.2 ppt warrants a certified drinking water filter for daily water consumption.