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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
26–50 of 1,134Tinley Park
IL0314910 · 56,703 served
Oak Park
IL0312250 · 54,583 served
Wheaton
IL0431050 · 53,970 served
Normal
IL1130900 · 52,736 served
Romeoville
IL1970900 · 50,458 served
Hoffman Estates
IL0311290 · 50,179 served
Plainfield
IL1970800 · 50,000 served
Downers Grove
IL0430300 · 49,425 served
Glenview
IL0311020 · 47,856 served
O Fallon
IL1631100 · 46,603 served
Il American-alton
IL1195150 · 46,127 served
Elmhurst
IL0430350 · 45,000 served
Dekalb
IL0370100 · 45,000 served
Moline
IL1610450 · 44,500 served
Lombard
IL0430600 · 44,476 served
Buffalo Grove
IL0314180 · 43,212 served
Quincy
IL0010650 · 42,000 served
Bartlett
IL0314120 · 41,500 served
Mount Prospect
IL0311980 · 41,000 served
Crystal Lake
IL1110150 · 40,661 served
Carol Stream
IL0430200 · 39,854 served
Park Ridge
IL0312460 · 39,800 served
Wheeling
IL0314970 · 39,725 served
Streamwood
IL0313060 · 39,577 served
Rock Island
IL1610650 · 39,018 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