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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
676–700 of 1,134Warsaw
IL0670650 · 1,480 served
Mount Carroll
IL0150200 · 1,479 served
North Pekin
IL1790550 · 1,478 served
Bethany
IL1390100 · 1,475 served
Hodgkins
IL0311260 · 1,472 served
Garden Home Sd
IL0315620 · 1,472 served
Green Oaks
IL0970040 · 1,470 served
Four Seasons Mhp
IL0075185 · 1,468 served
Silvis Heights Water Corp
IL1615750 · 1,450 served
Oakbrook Terrace
IL0430750 · 1,440 served
Crystal Lawns Addition Improvement Assoc
IL1975480 · 1,435 served
Cerro Gordo
IL1470100 · 1,433 served
South Fulton Water District
IL0570010 · 1,430 served
Devils Kitchen Water District
IL1995160 · 1,428 served
Durand
IL2010100 · 1,427 served
Wynstone Water Company
IL0970080 · 1,424 served
York Township Water System
IL0430010 · 1,423 served
Gridley
IL1130600 · 1,411 served
Pembroke Township
IL0910010 · 1,410 served
Onarga
IL0750700 · 1,409 served
Grandview
IL1670500 · 1,405 served
Murrayville-woodson Water Commission
IL1375150 · 1,403 served
Sunset Mhp
IL0310080 · 1,400 served
Centralia Correctional Site
IL0275600 · 1,397 served
Colchester
IL1090200 · 1,395 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