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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
776–800 of 1,134Danvers
IL1130450 · 1,183 served
Valier
IL0550600 · 1,182 served
Walnut Hill
IL1210600 · 1,180 served
Minier
IL1790450 · 1,180 served
South Barrington
IL0310200 · 1,175 served
Divernon
IL1670450 · 1,172 served
Mechanicsburg-buffalo Water Commission
IL1675150 · 1,170 served
Kingston
IL0370250 · 1,160 served
Atwood
IL0414060 · 1,155 served
Malta
IL0370350 · 1,143 served
Gorham
IL0770350 · 1,143 served
Prospect Water District
IL1655110 · 1,140 served
Mounds
IL1530150 · 1,135 served
Prairie Path Water Company-ferson Creek
IL0895800 · 1,134 served
Oquawka
IL0710300 · 1,125 served
Johnsburg No.2
IL1115080 · 1,124 served
Royalton
IL0555030 · 1,118 served
Flanagan
IL1050400 · 1,110 served
Oraville Water District
IL0775250 · 1,108 served
Il American-valley Marina
IL0935100 · 1,102 served
Greenfield
IL0610150 · 1,097 served
Griggsville
IL1490300 · 1,097 served
Worden
IL1191200 · 1,096 served
Heartville Pwd
IL0495200 · 1,092 served
Crossville
IL1930150 · 1,091 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