Illinois drinking water quality
Illinois has 5,097 active public water systems serving 12.6 million people. 2,544 of them, 50%, had at least one EPA violation in the past three years, 1,203 have an unresolved violation today, and 180 are designated serious violators by the EPA.
Active systems
5,097
in 102 counties
People served
12.6M
1,788 community systems serve 12.1M
Violations, past 3 years
2,544
50% of active systems
Serious violators
180
160 systems carry a health flag
Largest counties
All 102 countiesLargest community water systems
All 5,097 systems| System | Serves | Status |
|---|---|---|
| Chicago Cook County |
2,721,308 | |
| Aurora Kane County |
183,000 | |
| Joliet Will County |
160,000 | |
| Naperville DuPage County |
156,406 | |
| IL American-Champaign Champaign County |
150,000 | |
| Rockford Winnebago County |
147,051 | |
| IL American-Peoria Peoria County |
137,575 | |
| IL American-East ST Louis St. Clair County |
131,368 | |
| Springfield Sangamon County |
117,444 | |
| Elgin Kane County |
114,797 |
About the Illinois data
Retrieved from EPA ECHO on Oct 11, 2026. EPA records for Illinois systems do not include town names, so searches here match on ZIP code, street address, or county.