States → Illinois
State profile · EPA SDWIS + UCMR5
Illinois Drinking Water Quality
5,117 public water systems serve 12,576,876 people across Illinois, with every Safe Drinking Water Act violation and UCMR5 PFAS result on record.
- 5,117
- Water systems
- 355,322
- Total violations
- 80.8%
- Systems w/ a violation
- 40.9%
- PFAS detection rate
The verdict
Across Illinois, 4,134 of 5,117 water systems (80.8%) carry at least one EPA violation, and 199 of 487 UCMR5-tested systems show PFAS.
- 355,322
- Total EPA violations on record
- 15%
- Health-based (MCL / treatment)
- 80.8%
- Systems with ≥1 violation
- 40.9%
- UCMR5 PFAS detection rate
Water Systems
5,117
Total Violations
355,322
Violation Rate
80.8%
PFAS Detection
40.9%
199 of 487 tested
Violation Composition
How Illinois's 355,322 violations break down by type, per EPA SDWIS classification.
Health-based (52,932) Monitoring/Reporting (302,390)
| Metric | Value | Share |
|---|---|---|
| Public water systems | 5,117 | - |
| Population served | 12,576,876 | - |
| Total violations | 355,322 | 100% |
| Health-based violations | 52,932 | 14.9% |
| Systems with violations | 4,134 | 80.8% |
| PFAS detection rate | 199 of 487 | 40.9% |
Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement. Monitoring/reporting violations indicate procedural issues (missed tests, late reports) - not necessarily a contamination event.
Largest Water Systems
Chicago
Chicago, IL · 2,746,388 served
Aurora
Aurora, IL · 183,000 served
Joliet
Joliet, IL · 160,000 served
Naperville
Naperville, IL · 156,406 served
IL American-Champaign
Godfrey, IL · 150,000 served
Rockford
Rockford, IL · 147,051 served
IL American-Peoria
Godfrey, IL · 137,575 served
IL American-East St Louis
Godfrey, IL · 131,368 served
Springfield
Springfield, IL · 117,444 served
Elgin
Elgin, IL · 114,797 served
Waukegan
Waukegan, IL · 87,149 served
Cicero
Cicero, IL · 83,000 served
Aqua Illinois-Kankakee
Kankakee, IL · 80,000 served
Bloomington
Bloomington, IL · 77,610 served
Decatur
Decatur, IL · 76,122 served
Schaumburg
Schaumburg, IL · 75,750 served
Evanston
Evanston, IL · 74,486 served
IL American-West Suburban
Godfrey, IL · 73,978 served
Arlington Heights
Arlington Heights, IL · 73,320 served
Palatine
Palatine, IL · 70,875 served
Most Violations
#1 Skyview Estates Momence
7,512 #2 Windmill Estates Momence
5,042 #3 Carmel Montessori Academy Warrenville
4,386 #4 Criswell Court MHP Joliet
3,770 #5 Congregation Beth Judea Waukegan
3,204 #6 Christ Mission Lutheran Church Manhattan
3,123 #7 Save a Pet Waukegan
2,953 #8 American Precision Elctronics Carol Stream
2,881 #9 Forming America Ltd West Chicago
2,507 #10 Mother Teresa Catholic Academy Crete
2,381 #11 Taleem Ul Haq Plainfield
2,193 #12 Boley Tool and Machine Works Peoria
2,188 #13 Cog Hill Country Club Lemont
1,849 #14 Game Day Grill Downs
1,797 #15 Northfield Block Company 1 Morris
1,774 Counties in Illinois
Cook
427 systems · 5,304,996 served
· 21,728 violations
DuPage
207 systems · 861,775 served
· 15,779 violations
Lake
540 systems · 719,035 served
· 33,311 violations
Will
330 systems · 622,572 served
· 37,818 violations
Kane
191 systems · 592,544 served
· 12,844 violations
McHenry
307 systems · 271,051 served
· 11,554 violations
Madison
68 systems · 268,778 served
· 1,940 violations
St. Clair
54 systems · 258,141 served
· 3,100 violations
Winnebago
196 systems · 255,966 served
· 12,949 violations
Champaign
81 systems · 209,446 served
· 2,997 violations
Peoria
83 systems · 188,814 served
· 7,041 violations
Sangamon
68 systems · 183,628 served
· 1,245 violations
McLean
90 systems · 171,235 served
· 10,265 violations
Rock Island
120 systems · 164,178 served
· 6,591 violations
Tazewell
100 systems · 131,500 served
· 7,258 violations
LaSalle
174 systems · 112,392 served
· 13,172 violations
Macon
25 systems · 104,510 served
· 886 violations
DeKalb
57 systems · 100,590 served
· 2,730 violations
Kankakee
65 systems · 95,216 served
· 17,039 violations
Kendall
64 systems · 84,307 served
· 6,782 violations
Williamson
26 systems · 75,426 served
· 1,069 violations
Adams
25 systems · 67,920 served
· 2,040 violations
Vermilion
41 systems · 58,420 served
· 3,428 violations
Coles
16 systems · 57,953 served
· 520 violations
Jackson
24 systems · 56,580 served
· 761 violations
Grundy
63 systems · 52,209 served
· 12,515 violations
Knox
45 systems · 49,636 served
· 2,317 violations
Ogle
112 systems · 45,754 served
· 8,348 violations
Boone
56 systems · 45,698 served
· 2,853 violations
Macoupin
37 systems · 45,357 served
· 3,529 violations
Showing top 30 of 102 counties.
Drinking Water Guides
Frequently Asked Questions
How many water systems are in Illinois? ▼
Illinois has 5,117 public water systems serving approximately 12,576,876 people. These include community water systems, non-transient non-community systems, and transient non-community systems regulated under the Safe Drinking Water Act.
How many drinking water violations are in Illinois? ▼
Illinois has 355,322 total drinking water violations on record, with 52,932 classified as health-based violations. 80.8% of water systems in the state have at least one violation.
Has PFAS been found in Illinois drinking water? ▼
Of 487 water systems tested for PFAS in Illinois, 199 had PFAS detected, a 40.9% detection rate. PFAS are persistent "forever chemicals" that do not break down in the environment.
What is the violation rate for Illinois water systems? ▼
Illinois's violation rate is 80.8%. This measures the percentage of public water systems that have at least one recorded violation in the EPA SDWIS database, including both health-based and monitoring/reporting violations.
Where does this Illinois water data come from? ▼
All drinking water data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS is the federal database that tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources & Methodology
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.