Edwardsville Water Hardness & Quality Report (2026)

Edwardsville, Illinois, in Madison County in the Metro East region of the St. Louis metropolitan area, receives its municipal water from Illinois American Water, which draws from the Mississippi River near the confluence zone where the Missouri River joins from the northwest. This stretch of the Mississippi is one of the most mineralologically loaded freshwater corridors in the United States — carrying the combined dissolved mineral contributions of the Missouri River's 530,000-square-mile Rocky Mountain and Great Plains drainage together with the upper Mississippi's Midwest carbonate plain drainage.

The very hard 206 mg/L hardness directly reflects the combined Missouri-Mississippi mineral signature. The Missouri River contributes calcium and sulfate from Permian evaporite formations in Kansas and Nebraska, Cretaceous shale leachate from the Dakotas, and extensive loess plain drainage. The Mississippi above the confluence adds carbonate platform mineral load from Minnesota, Wisconsin, Iowa, and Illinois — all draining across extensive Silurian and Devonian dolomite plains. The resulting blended river water at the Alton, IL area intakes carries some of the highest dissolved mineral concentrations of any major US municipal surface water source.

At 206 mg/L, Edwardsville residents experience very hard water with significant daily consequences. Scale accumulates aggressively in all heated appliances — kettles, coffee makers, water heaters, and dishwashers all show rapid mineral buildup. White deposits appear on all water contact surfaces, dark sinks and tile surfaces show persistent calcium rings, and showerheads require monthly cleaning to maintain flow. A whole-house water softener is highly recommended for Edwardsville homeowners. An under-sink reverse osmosis unit further improves tap water taste and addresses the PFAS level of 7.2 ppt present in this supply area.