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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
126–150 of 1,134Mokena
IL1970600 · 19,887 served
Lake Zurich
IL0970850 · 19,759 served
Lake Forest
IL0970800 · 19,642 served
Mattoon
IL0290250 · 19,500 served
Homewood
IL0311350 · 19,463 served
Deerfield
IL0974340 · 19,196 served
Bellwood
IL0310150 · 19,156 served
Alsip
IL0310030 · 19,063 served
Il American-streator
IL0995030 · 19,000 served
Brookfield
IL0310330 · 18,776 served
Shorewood
IL1975080 · 18,645 served
Bensenville
IL0434140 · 18,537 served
Palos Hills
IL0312400 · 18,530 served
Sycamore
IL0370550 · 18,500 served
Franklin Park
IL0310960 · 18,467 served
Justice-willow Springs Water Commission
IL0315820 · 18,457 served
Round Lake
IL0971500 · 18,430 served
Matteson
IL0311800 · 18,293 served
North Aurora
IL0890600 · 18,261 served
Ottawa
IL0990800 · 18,097 served
Hinsdale
IL0434520 · 17,900 served
Cary
IL1110100 · 17,826 served
Lemont
IL0311620 · 17,500 served
Charleston
IL0290100 · 17,286 served
Morton
IL1790500 · 17,111 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