Loading water data...
Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Compare water quality across 18 counties in Illinois
18 counties ranked by average water quality score
| Rank | County | Avg Score | Grade | Cities | Population | Score Range |
|---|---|---|---|---|---|---|
| 1 | Champaign County | 100 | A | 1 | 150,000 | 100 - 100 |
| 2 | Macon County | 99 | A | 1 | 76,122 | 99 - 99 |
| 3 | McLean County | 96 | A | 2 | 130,346 | 94 - 97 |
| 4 | Adams County | 96 | A | 1 | 42,000 | 96 - 96 |
| 5 | DuPage County | 95 | A | 7 | 427,148 | 87 - 100 |
| 6 | Rock Island County | 95 | A | 2 | 83,518 | 92 - 97 |
| 7 | Sangamon County | 95 | A | 1 | 117,444 | 95 - 95 |
| 8 | Cook County | 92 | A | 22 | 3,884,861 | 55 - 100 |
| 9 | Lake County | 92 | A | 4 | 177,367 | 78 - 100 |
| 10 | Madison County | 91 | A | 1 | 33,572 | 91 - 91 |
| 11 | McHenry County | 90 | A | 2 | 71,361 | 80 - 100 |
| 12 | Kendall County | 89 | B | 1 | 38,169 | 89 - 89 |
| 13 | Will County | 83 | B | 3 | 260,458 | 61 - 99 |
| 14 | Peoria County | 81 | B | 1 | 137,575 | 81 - 81 |
| 15 | Kane County | 79 | C | 4 | 368,883 | 63 - 100 |
| 16 | DeKalb County | 79 | C | 1 | 40,290 | 79 - 79 |
| 17 | Knox County | 74 | C | 1 | 31,620 | 74 - 74 |
| 18 | Winnebago County | 73 | C | 1 | 147,051 | 73 - 73 |
7 cities • 427,148 residents
22 cities • 3,884,861 residents
4 cities • 177,367 residents
3 cities • 260,458 residents
4 cities • 368,883 residents
See all 18 counties in the ranking table above
Our county-level water quality analysis aggregates data from municipal water systems across Illinois. Each county's score represents the average water quality across all analyzed cities within that county, weighted by population served.
With 18 counties and 56 cities analyzed, this data helps residents understand regional water quality patterns in Illinois. County scores range from 55/100 to 100/100, reflecting the diversity of water sources and treatment infrastructure across the state.
All analyzed counties in Illinois maintain average scores above 70, indicating generally acceptable water quality standards statewide. Individual city scores may vary, so residents should still review their specific city's report.