Bloomington Water Hardness & Quality Report (2026)

Bloomington, Illinois — the McLean County seat in central Illinois (paired with Normal and home of Illinois State University and Illinois Wesleyan University) — draws its municipal water supply from Lake Bloomington (an impoundment on Money Creek in McLean County) and Evergreen Lake (Six Mile Creek impoundment), jointly operated by the City of Bloomington and Town of Normal Water Department. These two reservoirs are the primary surface water supply for the Bloomington-Normal metropolitan area. Water hardness in Bloomington measures 191.5 mg/L — classified as hard.

Bloomington's hard supply reflects central Illinois's geology of the McLean County reservoir watersheds. Money Creek and Six Mile Creek drain the McLean County glacial till plain — the thick Quaternary Illinoian and Wisconsin glacial till overlying the Mississippian Salem Limestone and Warsaw Formation limestone of the Illinois Basin (the same carboniferous carbonate belt that underlies southern and central Illinois). The glacial till itself is calcareous — derived primarily from grinding the underlying limestone and dolomite bedrock. Leachate from calcareous glacial till and direct dissolution of the Mississippian Ullin Limestone and Salem Limestone karst features contribute substantial dissolved calcium to the Money Creek and Six Mile Creek watersheds, producing the hard finished supply.

At 191.5 mg/L, Bloomington residents face regular hard water challenges. Scale deposits form on faucet aerators, showerheads, and appliances within weeks — monthly descaling with citric acid solution is standard maintenance. City of Bloomington/Town of Normal Water Department consistently delivers water meeting all Illinois EPA and federal EPA Safe Drinking Water Act requirements.