Sterling Water Hardness & Quality Report (2026)

Illinois American Water – Sterling supplies water to about 15,000 residents in Sterling, Illinois, located in Whiteside County along the Rock River. The utility's supply comes entirely from groundwater, drawn through wells that tap into local aquifers. Treatment occurs at the Sterling facility, where phosphate is used for corrosion control, a method deemed optimal by the Illinois EPA. While the overall watershed is the Rock River in northwest Illinois, the water's journey is underground, interacting with subsurface geology rather than surface flows.

The region's geology features northern Illinois bedrock composed of Paleozoic carbonates, specifically dolomite and limestone. These rocks, when weathered, release minerals into the water. Additionally, glacial deposits from the Pleistocene epoch that lie atop the bedrock contribute further dissolved minerals. This combination of bedrock and glacial till creates aquifers yielding a characteristically hard water supply, rich in calcium and magnesium ions, which significantly impacts the water's overall mineral content.

This hard water can lead to scale buildup within pipes, water heaters, and dishwashers, decreasing their efficiency and shortening their lifespan. You might notice laundry feeling stiff, and soap won't lather as readily, often necessitating the use of more detergent. To combat these issues and protect your plumbing, regular descaling of fixtures and appliances is advised, and installing a water softener is highly recommended. The utility also notes treatment with phosphate for corrosion control, and five contaminants were detected above EPA health guidelines: Gross Alpha Activity, Bromoform, Bromodichloromethane, Dichloroacetic Acid, and combined Radium.