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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
326–350 of 1,134East Alton
IL1190200 · 5,786 served
Staunton
IL1171050 · 5,756 served
Mill Creek Pwd
IL0015300 · 5,755 served
Grandwood Park Subdivision - Lake Co Pw
IL0975600 · 5,751 served
Coal City
IL0630200 · 5,749 served
Wilmington
IL1971100 · 5,700 served
Fayette Water Company
IL0510010 · 5,608 served
Shelbyville
IL1730300 · 5,600 served
Lake Bluff
IL0970750 · 5,600 served
Spring Valley
IL0111000 · 5,582 served
Millstone Pwd
IL1515050 · 5,565 served
Monticello
IL1470350 · 5,548 served
Eastern Illinois University
IL0295500 · 5,500 served
Watseka
IL0750900 · 5,500 served
Northeast Mount Vernon Water Company
IL0810010 · 5,483 served
Northfield
IL0312100 · 5,470 served
Park City
IL0971400 · 5,425 served
Robbins
IL0312700 · 5,415 served
Pike County Pwd 1
IL1495000 · 5,375 served
Aqua Illinois-oak Brook
IL0430055 · 5,361 served
Highwood
IL0970550 · 5,335 served
Posen
IL0312520 · 5,331 served
Sangamon Valley Pwd
IL0195150 · 5,300 served
Genoa
IL0370150 · 5,298 served
Mitchell Pwd
IL1195210 · 5,253 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