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Private well testing in New Hampshire
A state overview with links to every New Hampshire county page we've published. Every fact has a source.
County pages
- Well water testing in Hillsborough County, NHArsenic in Hillsborough County private wells, New Hampshire's testing guidance, accredited labs near Manchester and Nashua, town testing rules, and who to contact, with sources.
- Well water testing in Rockingham County, NHArsenic, radon and other results from Rockingham County private wells, New Hampshire's testing guidance, accredited labs near the Seacoast, and who to contact, with sources.
New Hampshire at a glance
- Who's on a well: nearly half of New Hampshire residents get their water from a private well.1 NHDES's 2021 figure was about 46% of the population, roughly 520,000 people.2
- Rules: there's no statewide testing or treatment requirement for private wells, but some towns require testing for a certificate of occupancy.2
- Arsenic: NHDES estimates 25–30% of private residential wells have arsenic at 5 ppb or higher.3
- Radon: in state lab results from 2006 to August 2020, 30% of private wells were above NHDES's 2,000 pCi/L radon testing advisory level.2
- PFAS: NHDES has sampled private wells for PFAS since 2016 and takes sampling requests through the NH PFAS Response website.4
What NHDES recommends
Test for bacteria, nitrate and nitrite every year, and for arsenic, chloride, copper, fluoride, hardness, iron, lead, manganese, pH, radon, sodium, uranium and four PFAS every 3–5 years. Test before buying a home with a well, and test treated water after installing a treatment system.4 Use a lab accredited by NHELAP; the state's Accredited Laboratory Search is the official list.4 To understand your results, NHDES points to its Be Well Informed web tool.1
Guides for New Hampshire well owners
- Arsenic in well water: testing and treatment options
- Uranium and radon in well water
- How often to test a private well
- Whole-house vs. point-of-use treatment
- How to read your well water test results
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NHDES, "Private Wells." https://www.des.nh.gov/water/drinking-water/private-wells ↩↩
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Kernen, B., NHDES, "Private Wells in Portsmouth" (presentation, September 1, 2021), hosted by the City of Portsmouth. https://www.portsmouthnh.gov/sites/default/files/2021-09/Portsmouth%20SWAG%20Sep%201%202021%20DES.pdf ↩↩↩
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NHDES, "More Protective Arsenic Standard Will Reduce Risk for Many" (March 8, 2021). https://www.des.nh.gov/news-and-media/blog/more-protective-arsenic-standard-will-reduce-risk-many ↩
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NHDES, "Water Testing Guidance for Private Well Users" (April 2026). https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/labs-private-wells.pdf ↩↩↩