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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
751–775 of 1,134Albers
IL0270050 · 1,231 served
Warrensburg
IL1150500 · 1,230 served
Forrest
IL1050450 · 1,225 served
Il American-arbury
IL1975040 · 1,225 served
Hillcrest
IL1410250 · 1,224 served
Macon
IL1150250 · 1,205 served
Louisville
IL0250200 · 1,201 served
Downs
IL1130500 · 1,201 served
Windsor
IL1730550 · 1,200 served
Stillman Valley
IL1410550 · 1,200 served
Homer
IL0190300 · 1,200 served
Martinsville
IL0230150 · 1,200 served
St Anne
IL0910700 · 1,200 served
Laharpe
IL0670450 · 1,200 served
Nauvoo
IL0670500 · 1,200 served
Aqua Illinois-skyline (northern)
IL0895030 · 1,200 served
South Lawrence Water Corp
IL1010020 · 1,195 served
Waverly
IL1370450 · 1,194 served
Il American-glasford
IL1430350 · 1,193 served
Toulon
IL1750150 · 1,193 served
Camp Point
IL0010050 · 1,190 served
Dowell
IL0770250 · 1,188 served
Ferges Water District
IL1995050 · 1,185 served
Cuba
IL0570300 · 1,184 served
Il American-andalusia
IL1610050 · 1,184 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.
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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