New Hampshire water quality by county
10 counties with public water systems. Pick a county to see every system that serves it.
| County | Active systems | People served | Share with violations, 3 yr | Serious violators | Health flags |
|---|---|---|---|---|---|
| Belknap County | 256 | 71,091 | 1 | 1 | |
| Carroll County | 367 | 81,101 | 5 | 2 | |
| Cheshire County | 168 | 69,082 | 1 | 0 | |
| Coos County | 114 | 41,415 | 2 | 2 | |
| Grafton County | 269 | 106,381 | 3 | 2 | |
| Hillsborough County | 280 | 336,745 | 0 | 4 | |
| Merrimack County | 246 | 124,540 | 1 | 0 | |
| Rockingham County | 554 | 271,624 | 4 | 8 | |
| Strafford County | 132 | 108,137 | 1 | 0 | |
| Sullivan County | 65 | 33,176 | 0 | 2 |
under 30% 30 to 59% 60% and over
About this data
Share with violations counts any violation in the past three years, including monitoring and reporting lapses. Counts cover active systems; systems serving more than one county are counted in each.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The New Hampshire records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.