New Hampshire drinking water quality
New Hampshire has 2,451 active public water systems serving 1.2 million people. 805 of them, 33%, had at least one EPA violation in the past three years, 135 have an unresolved violation today, and 18 are designated serious violators by the EPA.
Active systems
2,451
in 10 counties
People served
1.2M
706 community systems serve 923K
Violations, past 3 years
805
33% of active systems
Serious violators
18
21 systems carry a health flag
Largest counties
All 10 counties| County | People served | Systems | With violations |
|---|---|---|---|
| Hillsborough | 336,745 | 280 | 96 |
| Rockingham | 271,624 | 554 | 153 |
| Merrimack | 124,540 | 246 | 79 |
| Strafford | 108,137 | 132 | 45 |
| Grafton | 106,381 | 269 | 117 |
| Carroll | 81,101 | 367 | 129 |
| Belknap | 71,091 | 256 | 72 |
| Cheshire | 69,082 | 168 | 48 |
| Coos | 41,415 | 114 | 48 |
| Sullivan | 33,176 | 65 | 18 |
Largest community water systems
All 2,451 systems| System | Serves | Status |
|---|---|---|
| Manchester Water Works Hillsborough County |
123,500 | |
| Pennichuck Water Works Hillsborough County |
88,853 | |
| Concord Water Dept Merrimack County |
44,215 | |
| Aquarion Water/nh Rockingham County |
34,000 | |
| Portsmouth Water Works Rockingham County |
33,000 | |
| Keene Water Dept Cheshire County |
30,000 | |
| Dover Water Dept Strafford County |
29,000 | |
| Merrimack Village Dist Hillsborough County |
25,500 | |
| Rochester Water Dept Strafford County |
25,000 | |
| Salem Water Dept Rockingham County |
21,080 |
About the New Hampshire data
Retrieved from EPA ECHO on Oct 11, 2026.