Lead in New Hampshire well water
In New Hampshire, 14% of 13,549 private wells tested between 2006 and 2020 had lead above the New Hampshire guidance level (15 ug/L), according to NH DHHS.
Lead in well water almost always comes from household plumbing and older fixtures, not the aquifer, and corrosive (low pH) well water makes it worse. There is no safe level for children; it harms brain development.
By county, from homeowner tests
Share of private wells above the state guidance level (15 ug/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Coos | 346 | 17% | 721 ug/L | |
| Cheshire | 375 | 17% | 205 ug/L | |
| Sullivan | 543 | 15% | 892 ug/L | |
| Hillsborough | 1,580 | 15% | 31,200 ug/L | |
| Carroll | 1,491 | 14% | 3,820 ug/L | |
| Rockingham | 1,737 | 13% | 15,100 ug/L | |
| Merrimack | 3,868 | 13% | 2,490 ug/L | |
| Grafton | 1,948 | 13% | 10,400 ug/L | |
| Belknap | 1,398 | 12% | 1,340 ug/L | |
| Strafford | 263 | 9% | 169 ug/L |
Towns with the highest share above the state level
- Derry, Rockingham County38% of 68 wells
- Windham, Rockingham County25% of 171 wells
- Sugar Hill, Grafton County24% of 38 wells
- Stoddard, Cheshire County22% of 49 wells
- Antrim, Hillsborough County22% of 64 wells
- Hollis, Hillsborough County22% of 92 wells
- Danbury, Merrimack County22% of 65 wells
- Milan, Coos County21% of 47 wells
- Tilton, Belknap County21% of 47 wells
- Alexandria, Grafton County21% of 96 wells
- Deering, Hillsborough County21% of 82 wells
- New Ipswich, Hillsborough County20% of 49 wells
- Kingston, Rockingham County20% of 64 wells
- Sunapee, Sullivan County20% of 169 wells
- New London, Merrimack County20% of 190 wells
- Colebrook, Coos County20% of 40 wells
- Grafton, Grafton County20% of 35 wells
- Epsom, Merrimack County20% of 116 wells
- Piermont, Grafton County20% of 46 wells
- Hill, Merrimack County19% of 36 wells
- Ossipee, Carroll County19% of 117 wells
- Wakefield, Carroll County19% of 64 wells
- Fitzwilliam, Cheshire County19% of 32 wells
- Chichester, Merrimack County19% of 150 wells
- Newbury, Merrimack County19% of 211 wells
By county, from individual samples
Public monitoring samples against the EPA limit (15 ug/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Sullivan | 32 | 50% | 6% | 0 | 600 ug/L |
| Strafford | 56 | 48% | 4% | 0 | 200 ug/L |
| Merrimack | 146 | 58% | 2% | 0.09 | 51 ug/L |
| Grafton | 73 | 36% | 1% | 0 | 20 ug/L |
| Hillsborough | 208 | 61% | 0% | 0 | 8.73 ug/L |
| Rockingham | 183 | 50% | 0% | 0 | 10.2 ug/L |
| Carroll | 69 | 36% | 0% | 0 | 5.69 ug/L |
| Coos | 37 | 16% | 0% | 0 | 10 ug/L |
Sources
- NH DHHS WISDOM private well summaries: Town summaries of private well tests run by the New Hampshire Public Health Laboratories, published by NH DHHS through the WISDOM environmental public health tracking portal. Exceedance shares use New Hampshire guidance levels, which are stricter than EPA for arsenic (5 ug/L), manganese (0.3 mg/L), radon (2,000 pCi/L) and sodium (20 mg/L). Statistics for small counts are suppressed (*). Retrieved September 3, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. lead counts and shares are listed on each county and town page with their sources.