Copper in New Hampshire well water
In New Hampshire, 13% of 13,478 private wells tested between 2006 and 2020 had copper above the New Hampshire guidance level (1.3 mg/L), according to NH DHHS.
Copper leaches from pipes when water is acidic. Above 1.3 mg/L it causes stomach upset, and long-term exposure can harm the liver and kidneys. Blue-green stains on fixtures are the giveaway.
By county, from homeowner tests
Share of private wells above the state guidance level (1.3 mg/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Coos | 346 | 15% | 10.1 mg/L | |
| Carroll | 1,488 | 14% | 18.2 mg/L | |
| Hillsborough | 1,576 | 14% | 315 mg/L | |
| Merrimack | 3,853 | 13% | 14.2 mg/L | |
| Grafton | 1,939 | 13% | 58.1 mg/L | |
| Cheshire | 372 | 13% | 12.3 mg/L | |
| Strafford | 261 | 11% | 12.8 mg/L | |
| Sullivan | 541 | 11% | 10.4 mg/L | |
| Rockingham | 1,723 | 11% | 32.1 mg/L | |
| Belknap | 1,379 | 10% | 15.8 mg/L |
Towns with the highest share above the state level
- Effingham, Carroll County34% of 38 wells
- Temple, Hillsborough County28% of 61 wells
- Madison, Carroll County27% of 34 wells
- Milan, Coos County26% of 47 wells
- Warren, Grafton County24% of 38 wells
- Danbury, Merrimack County23% of 65 wells
- Andover, Merrimack County22% of 140 wells
- Derry, Rockingham County22% of 68 wells
- Sutton, Merrimack County22% of 132 wells
- Rumney, Grafton County21% of 108 wells
- Windham, Rockingham County21% of 171 wells
- New Ipswich, Hillsborough County20% of 49 wells
- Wakefield, Carroll County20% of 64 wells
- Ossipee, Carroll County20% of 117 wells
- Dublin, Cheshire County20% of 61 wells
- Amherst, Hillsborough County20% of 61 wells
- Bradford, Merrimack County19% of 110 wells
- Tamworth, Carroll County19% of 100 wells
- Deering, Hillsborough County19% of 81 wells
- Goffstown, Hillsborough County18% of 103 wells
- Chichester, Merrimack County18% of 149 wells
- Alexandria, Grafton County18% of 95 wells
- Wilmot, Merrimack County17% of 87 wells
- Kingston, Rockingham County17% of 64 wells
- New Boston, Hillsborough County17% of 59 wells
By county, from individual samples
Public monitoring samples against the EPA limit (1.3 mg/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Hillsborough | 85 | 71% | 4% | 0.005 | 6.82 mg/L |
| Carroll | 69 | 42% | 3% | 0 | 6.91 mg/L |
| Merrimack | 135 | 81% | 1% | 0.005 | 7 mg/L |
| Strafford | 54 | 78% | 0% | 0 | 0.42 mg/L |
| Rockingham | 155 | 58% | 0% | 0 | 1.12 mg/L |
| Sullivan | 31 | 55% | 0% | 0.006 | 1.26 mg/L |
| Grafton | 70 | 39% | 0% | 0 | 0.807 mg/L |
| Coos | 36 | 19% | 0% | 0 | 0.69 mg/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. copper counts and shares are listed on each county and town page with their sources.