Iron in New Hampshire well water
In New Hampshire, 18% of 17,420 private wells tested between 2006 and 2020 had iron above the New Hampshire guidance level (300 ug/L), according to NH DHHS.
Iron is a nuisance rather than a health hazard: rust stains, metallic taste, and clogged fixtures above 300 ug/L. It often occurs with manganese and can feed iron bacteria that foul plumbing.
By county, from homeowner tests
Share of private wells above the state guidance level (300 ug/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Cheshire | 428 | 24% | 69,000 ug/L | |
| Belknap | 1,481 | 24% | 66,400 ug/L | |
| Sullivan | 610 | 20% | 59,600 ug/L | |
| Grafton | 2,109 | 20% | 48,600 ug/L | |
| Merrimack | 4,212 | 20% | 74,200 ug/L | |
| Coos | 431 | 19% | 22,300 ug/L | |
| Carroll | 1,639 | 16% | 13,600 ug/L | |
| Strafford | 440 | 15% | 33,200 ug/L | |
| Hillsborough | 3,290 | 15% | 87,800 ug/L | |
| Rockingham | 2,780 | 13% | 36,900 ug/L |
Towns with the highest share above the state level
- Epsom, Merrimack County40% of 132 wells
- Tilton, Belknap County38% of 47 wells
- Washington, Sullivan County37% of 100 wells
- Mont Vernon, Hillsborough County37% of 41 wells
- Gilmanton, Belknap County36% of 182 wells
- Pittsfield, Merrimack County36% of 56 wells
- Chichester, Merrimack County36% of 174 wells
- Stoddard, Cheshire County34% of 53 wells
- Barnstead, Belknap County34% of 173 wells
- Franklin, Merrimack County33% of 73 wells
- Rindge, Cheshire County33% of 113 wells
- Hebron, Grafton County32% of 91 wells
- Bristol, Grafton County31% of 71 wells
- Wakefield, Carroll County29% of 72 wells
- Orford, Grafton County29% of 38 wells
- Whitefield, Coos County29% of 38 wells
- Raymond, Rockingham County28% of 50 wells
- Ossipee, Carroll County28% of 126 wells
- Fitzwilliam, Cheshire County28% of 36 wells
- Sanbornton, Belknap County27% of 133 wells
- Northwood, Rockingham County27% of 145 wells
- Rumney, Grafton County27% of 116 wells
- Groton, Grafton County27% of 30 wells
- Canterbury, Merrimack County26% of 161 wells
- Thornton, Grafton County26% of 124 wells
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. iron counts and shares are listed on each county and town page with their sources.