Ottawa Water Hardness & Quality Report (2026)

The Ottawa Municipal Water Company, also known as the City of Ottawa Water Division, serves approximately 19,024 residents in Ottawa, Illinois, located in LaSalle County along the Illinois River. Water is sourced exclusively from local groundwater via wells, with operations managed from 828 East Norris Drive. Superintendent Dave Erwin oversees the City of Ottawa Public Works water department, reachable at 815-434-0025. Annual Drinking Water Quality Reports are archived on the official city website, cityofottawa.org.

Ottawa's supply draws from glacial drift aquifers and deeper bedrock aquifers in the Illinois River Valley region, underlain by Paleozoic limestone and dolomite from the Ordovician and Silurian periods, including the Maquoketa Group and Galena-Platteville formations. These carbonate rocks are rich in calcium and magnesium; as groundwater percolates through fractures and porous glacial till, it dissolves these minerals, producing elevated dissolved solids typical of northern Illinois groundwater and a characteristically hard supply.

Very hard water leads to significant scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan while increasing energy costs. White deposits on fixtures and soap scum are common. Regular vinegar descaling, installing scale inhibitors, or a water softener is recommended — softeners typically regenerate every four days at average use. Recent public notices flag potential contaminants including vinyl chloride, manganese, bacteria and viruses, and 1,4-dioxane in the groundwater; treatment involves disinfection and likely aeration or filtration for iron and manganese.