Water Quality · New Hampshire
Best Water Quality Counties in New Hampshire 2026
Ranked by EPA drinking water health violations.
Top 10 — Water Quality in New Hampshire
Score reflects water quality only — not overall county quality.
All New Hampshire Counties — Water Quality Rankings
10 counties ranked by water quality score. Overall Score shown for context.
| # | County | Water Quality Score | Overall Score |
|---|---|---|---|
| 1 | Sullivan County, NH | 57.8 | 42.8 |
| 2 | Cheshire County, NH | 51.2 | 43.4 |
| 3 | Coos County, NH | 49.9 | 41.2 |
| 4 | Hillsborough County, NH | 41.5 | 39.3 |
| 5 | Strafford County, NH | 35.9 | 40.1 |
| 6 | Grafton County, NH | 27.4 | 44.5 |
| 7 | Rockingham County, NH | 26.4 | 48.9 |
| 8 | Merrimack County, NH | 20.5 | 43.6 |
| 9 | Belknap County, NH | 13.5 | 38.3 |
| 10 | Carroll County, NH | 7.5 | 49 |