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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 13 counties in Idaho
13 counties ranked by average water quality score
| Rank | County | Avg Score | Grade | Cities | Population | Score Range |
|---|---|---|---|---|---|---|
| 1 | Madison County | 93 | A | 1 | 31,441 | 93 - 93 |
| 2 | Kootenai County | 91 | A | 2 | 93,113 | 87 - 95 |
| 3 | Bannock County | 91 | A | 1 | 56,320 | 91 - 91 |
| 4 | Banneville County | 86 | A- | 1 | 15,570 | 86 - 86 |
| 5 | Elmore County | 86 | A- | 1 | 14,308 | 86 - 86 |
| 6 | Latah County | 80 | B+ | 1 | 26,047 | 80 - 80 |
| 7 | Canyon County | 78 | B | 2 | 160,196 | 72 - 83 |
| 8 | Jerome County | 77 | B | 1 | 12,137 | 77 - 77 |
| 9 | Bonneville County | 75 | B | 2 | 82,512 | 70 - 79 |
| 10 | Twin Falls County | 74 | B- | 1 | 51,807 | 74 - 74 |
| 11 | Ada County | 71 | B- | 5 | 421,043 | 66 - 80 |
| 12 | Nez Perce County | 71 | B- | 1 | 34,203 | 71 - 71 |
| 13 | Bingham County | 66 | C+ | 1 | 12,346 | 66 - 66 |
1 cities • 31,441 residents
2 cities • 93,113 residents
1 cities • 56,320 residents
1 cities • 15,570 residents
1 cities • 14,308 residents
1 cities • 26,047 residents
2 cities • 160,196 residents
1 cities • 12,137 residents
2 cities • 82,512 residents
1 cities • 51,807 residents
5 cities • 421,043 residents
1 cities • 34,203 residents
See all 13 counties in the ranking table above
Our county-level water quality analysis aggregates data from municipal water systems across Idaho. Each county's score represents the average water quality across all analyzed cities within that county, weighted by population served.
With 13 counties and 20 cities analyzed, this data helps residents understand regional water quality patterns in Idaho. County scores range from 66/100 to 95/100, reflecting the diversity of water sources and treatment infrastructure across the state.
Currently, 1 counties in Idaho have average scores below 70, indicating potential water quality concerns. Residents in these areas should review their city's specific report and consider water filtration options.