New Hampshire Water Quality
Drinking water data for all 10 counties.
Avg Water Score
33.2
State Grade
F
Counties with Data
10
of 10 total
All New Hampshire Counties
| County | Water Score |
|---|---|
| Sullivan County | 57.8 |
| Cheshire County | 51.2 |
| Coos County | 49.9 |
| Hillsborough County | 41.5 |
| Strafford County | 35.9 |
| Grafton County | 27.4 |
| Rockingham County | 26.4 |
| Merrimack County | 20.5 |
| Belknap County | 13.5 |
| Carroll County | 7.5 |
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Frequently Asked Questions
Which county in New Hampshire has the best water quality?
Sullivan County has the highest water quality score in New Hampshire at 57.8/100 (Grade: C), based on EPA SDWIS data.
Which county in New Hampshire has the most water violations?
Carroll County has among the lowest water quality scores in New Hampshire at 7.5/100. See the individual county page for detailed violation history.
Is the tap water safe to drink in New Hampshire?
New Hampshire has an average water quality score of 33.2/100 based on EPA Safe Drinking Water Act compliance data. Individual county scores vary — check your specific county's page for detailed information.
What contaminants are found in New Hampshire water supplies?
Drinking water quality varies by county and water system. The EPA Safe Drinking Water Information System (SDWIS) tracks violations for contaminants like lead, nitrates, bacteria, and disinfection byproducts. See individual county pages for specific contaminant and violation history.
Data Source
Water quality data sourced from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.
Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.