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Illinois Water Quality
1,134
Utilities in database
12.0M
Residents served
20%
On private wells
3
Key contaminants tracked
Drinking Water in Illinois
Illinois has 1,134 community water systems serving approximately 12.0 million residents. Primary water sources include groundwater. The most commonly reported contaminants include lead, disinfection byproducts, nitrates. 20% of Illinois residents rely on private wells. IEPA holds primary enforcement authority under the Safe Drinking Water Act.
Utilities in Illinois
51–75 of 1,134Oswego
IL0930150 · 38,169 served
Addison
IL0430050 · 38,017 served
Carpentersville
IL0890200 · 37,983 served
Hanover Park
IL0314480 · 37,470 served
Calumet City
IL0310390 · 37,000 served
North Park Pwd
IL2015500 · 35,580 served
Elk Grove Village
IL0314400 · 34,700 served
Northbrook
IL0312070 · 34,407 served
Woodridge
IL0431250 · 33,566 served
Vernon Hills - Lake Co Pw
IL0971750 · 33,207 served
Glendale Heights
IL0430400 · 33,176 served
St Charles
IL0894830 · 33,103 served
Il American-pekin
IL1795040 · 31,731 served
Galesburg
IL0950200 · 31,620 served
Mundelein
IL0971150 · 31,500 served
Algonquin
IL1110050 · 30,700 served
Gurnee
IL0970350 · 30,193 served
Highland Park
IL0970500 · 30,176 served
Aqua Illinois-vermilion County
IL1835120 · 30,106 served
Aqua Illinois-north Maine Utilities
IL0315350 · 30,043 served
South Stickny Sd
IL0317370 · 30,000 served
Ej Water Cooperative
IL0790010 · 29,720 served
Collinsville
IL1194280 · 29,500 served
Niles
IL0312010 · 29,350 served
Lansing
IL0311590 · 29,076 served
Key Contaminant Concerns in Illinois
Lead
Lead is a naturally occurring heavy metal that was widely used in plumbing infrastructure until it was banned for new installations in 1986. An estimated 9.2 million lead service lines still connect homes to public water mains across the United States, along with millions of homes with lead solder in their internal plumbing.
Nitrates
Nitrate (NO₃⁻) is a nitrogen-containing compound that forms naturally through the decomposition of organic matter. At elevated concentrations — almost always from human activity — nitrate interferes with the blood's ability to carry oxygen. The United States produces over 23 million tons of nitrogen fertilizer annually, making agricultural runoff the dominant source of nitrate contamination.
DBPs
When utilities add chlorine to water to kill pathogens, it reacts with dissolved organic matter — leaves, algae, soil — to produce disinfection byproducts (DBPs). Over 600 DBPs have been identified. The EPA regulates two groups: total trihalomethanes (TTHMs, including chloroform) and haloacetic acids (HAA5). DBP levels tend to be highest in surface water systems and in warm months when organic matter is elevated.
Illinois Water FAQs
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Data source: Utility data from EPA SDWIS. 1,134 active community water systems ingested. CCR contaminant data ingestion in progress.
Last updated: 2026-04-17