Radon in New Hampshire well water
In New Hampshire, 50% of 5,561 private wells tested between 2006 and 2020 had radon above the New Hampshire guidance level (2,000 pCi/L), according to NH DHHS.
Radon is a radioactive gas released from bedrock into well water. It escapes into household air during showers and washing, where inhaling it raises lung cancer risk. EPA has no enforceable water MCL; New Hampshire recommends treatment above 2,000 pCi/L, and many states use 4,000 pCi/L.
Check your radon number
Type the value from your lab report. It is compared to the New Hampshire guidance level and the EPA limit, the same way the full interpretation does it.
Test your New Hampshire well for radon
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
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Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes radon.
Where to get a well tested for radon in New Hampshire: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (2,000 pCi/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Above state level | Wells tested | Highest |
|---|---|---|---|
| Sullivan | 148 | 35,000 pCi/L | |
| Strafford | 99 | 670,000 pCi/L | |
| Rockingham | 655 | 120,000 pCi/L | |
| Cheshire | 78 | 36,000 pCi/L | |
| Merrimack | 2,140 | 330,000 pCi/L | |
| Hillsborough | 695 | 380,000 pCi/L | |
| Grafton | 496 | 40,701 pCi/L | |
| Belknap | 577 | 71,000 pCi/L | |
| Carroll | 673 | 150,000 pCi/L |
Towns with the highest share above the state level
- Hooksett, Merrimack County90% of 195 wells
- Goffstown, Hillsborough County83% of 65 wells
- Hudson, Hillsborough County81% of 47 wells
- Wakefield, Carroll County79% of 33 wells
- Pelham, Hillsborough County78% of 74 wells
- Sunapee, Sullivan County78% of 99 wells
- Chichester, Merrimack County75% of 88 wells
- Bow, Merrimack County75% of 394 wells
- New London, Merrimack County71% of 139 wells
- Atkinson, Rockingham County70% of 40 wells
- Pembroke, Merrimack County70% of 53 wells
- Derry, Rockingham County69% of 42 wells
- Londonderry, Rockingham County68% of 56 wells
- Nottingham, Rockingham County67% of 52 wells
- Windham, Rockingham County67% of 82 wells
- Deerfield, Rockingham County67% of 66 wells
- New Ipswich, Hillsborough County67% of 33 wells
- Loudon, Merrimack County65% of 102 wells
- Tamworth, Carroll County65% of 34 wells
- Epsom, Merrimack County64% of 53 wells
- Concord, Merrimack County63% of 181 wells
- Newbury, Merrimack County61% of 140 wells
- Dublin, Cheshire County61% of 31 wells
- Barnstead, Belknap County61% of 49 wells
- Temple, Hillsborough County61% of 43 wells
By county, from individual samples
Public monitoring samples against the EPA limit; counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Carroll | no limit | 35 | 100% | 3,800 | 83,600 pCi/L |
| Hillsborough | no limit | 36 | 100% | 1,350 | 64,000 pCi/L |
| Merrimack | no limit | 105 | 99% | 4,900 | 910,000 pCi/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. radon counts and shares are listed on each county and town page with their sources.