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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
401–425 of 1,134Woodhaven
IL1035100 · 4,100 served
Millstadt
IL1630850 · 4,071 served
Smithton
IL1631300 · 4,006 served
Wasco Sd
IL0890110 · 4,000 served
Burnham
IL0310360 · 3,989 served
North East Central Pwd
IL1195280 · 3,975 served
Coal Valley Pwd
IL1995250 · 3,960 served
Hamilton County Water District
IL0651000 · 3,958 served
Rosemont
IL0312760 · 3,952 served
Marshall
IL0230100 · 3,947 served
Corinth Pwd
IL1995120 · 3,927 served
South Chicago Heights
IL0312940 · 3,924 served
Saline Valley Conservancy District
IL1655300 · 3,921 served
Westville
IL1830950 · 3,917 served
Metamora
IL2030350 · 3,895 served
Coal Valley
IL1614260 · 3,873 served
Wonder Lake
IL1115750 · 3,870 served
Rochester
IL1671000 · 3,856 served
Red Bud
IL1570450 · 3,804 served
Greene County Rwd
IL0610020 · 3,786 served
Pleasant Valley Pwd
IL1435470 · 3,783 served
Embarras Area Water District
IL0290020 · 3,750 served
Gillespie
IL1170400 · 3,737 served
Lcpw - Pekara Subdivision
IL0975900 · 3,711 served
Rend Lake Inter-city Water System
IL0555100 · 3,650 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