Coralville Water Hardness & Quality Report (2026)

Coralville, Iowa, in Johnson County — a Johnson County city directly adjacent to Iowa City and the University of Iowa campus, named for the Devonian coral fossils famously exposed in local limestone quarries (the Coral Ridge formation — the geological origin of the name), a college-town suburb heavily influenced by the University of Iowa medical and research complex — receives its municipal water from the Iowa City Water Division or Coralville Water Utility, which draws from the Iowa River at the Iowa City-Coralville intake in the Iowa River valley.

The extremely hard 343.5 mg/L hardness and very high TDS of 882.1 mg/L reflect the Iowa River watershed's extreme Devonian carbonate geology — Coralville literally sits on and above the Devonian Iowa Limestone that gives the city its name. The Iowa River drains eastern Iowa's Iowa Drift Plain — underlain by the Devonian Coralville Formation (thick-bedded limestone), the Devonian Rapid Creek Formation, the Silurian Niagara Group dolomite, and the Ordovician Galena Dolomite — a sequence of ancient Paleozoic marine carbonate platforms that extend beneath much of eastern Iowa. The Iowa Drift Plain's Pleistocene glacial till rich in Devonian and Silurian limestone clasts adds additional carbonate dissolution loading to the Iowa River, producing the consistently extremely hard water characteristic of the Iowa City-Coralville corridor.

At 343.5 mg/L with TDS 882 mg/L, Coralville's water is extremely hard. Scale forms very quickly on appliances and fixtures. A whole-house water softener is essential. The PFAS level of 7.1 ppt warrants a certified drinking water filter — the Iowa National Guard Iowa City installations, the University of Iowa hospital and research complex (laboratory chemical use), and the Johnson County agricultural chemical corridor contribute to the Iowa River's PFAS reading in this corridor.