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Radon in New Hampshire well water
USGS area-risk estimates for Radon in New Hampshire private wells, by county. Radon is a health hazard. Inhaling radon released from water is a lung-cancer risk, and there is no national groundwater grid for it — New Hampshire is the only state with a published model. A water radon test, paired with an air test, is the only way to measure your own exposure.
How common is Radon in New Hampshire?
New Hampshire has a modeled Radon estimate for 10 counties, with a county-area average of 31%.
These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
What is Radon?
Radon is a colorless, odorless radioactive gas produced by the decay of uranium and radium in bedrock. It dissolves into well water and is released into the air when water is agitated — showering, washing dishes, or doing laundry.
Health effects of Radon
Radon is a health hazard. Inhaling radon released from water (and from soil gas) is a lung-cancer risk; swallowing radon in water carries a smaller internal-organ cancer risk. Most household radon comes from soil gas, with well water a secondary contributor.
Symptoms & signs
- No immediate symptoms
- Long-term risk is lung cancer from inhaled radon
Who is most at risk
- Smokers (radon multiplies their lung-cancer risk)
- Households with high indoor-air radon
Radon's risk is entirely long-term (cancer) — there is no acute illness from radon in water.
How Radon gets into a well
Radon forms continuously from uranium and radium in the surrounding rock and dissolves into groundwater. No well construction method prevents it; it comes from the geology the well draws from.
Where Radon is common
Radon in well water is highest where bedrock is uranium-rich granite or shale — New England (notably New Hampshire and Maine), the Rocky Mountains, and parts of the Appalachians. Only New Hampshire publishes a modeled surface for private-well radon; everywhere else, test your own well.
Highest Radon risk counties in New Hampshire
Counties with the highest modeled Radon area-risk in New Hampshire. These are county-area estimates, not a measurement of any single well.
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Find a New Hampshire-certified lab
Get your well tested for Radon at a New Hampshire-certified laboratory.
How to remove Radon: treatment options
Aeration (point-of-entry)
Whole-house (point-of-entry)Physically strips the radon gas out of the water by bubbling or spraying air through it; treats all water in the home and adds no chemicals or radioactive waste.
Higher upfront cost than carbon, but low operating cost and no waste-disposal issue.
Whole-house (point-of-entry) systems are a larger investment — typically into the thousands of dollars installed — and total cost varies widely with water chemistry, system type, and professional installation.
Granular activated carbon (GAC)
Whole-house (point-of-entry)Adsorbs radon as water passes through a whole-house carbon tank.
Radon accumulates on the carbon and the unit can itself become radioactive — siting and eventual disposal need care.
Costs are typical installed ranges that vary widely by system, water chemistry, region, and whether you install it yourself or hire a professional. Last reviewed 2026-06. Always confirm a device is certified (NSF/ANSI or WQA) for the specific contaminant.
Testing for Radon
- EPA proposed standard (never finalized)
- proposed MCL 300 pCi/L; alternative MCL (AMCL) 4,000 pCi/L with a multimedia mitigation programEPA proposed these limits in 1999 but has never finalized a radon-in-drinking-water rule, so there is no enforceable federal standard.
- Can you taste, smell, or see it?
- None — radon is colorless and odorless.
- Collecting a sample
- Radon needs special sample vials and a certified lab; pair a water-radon test with an indoor-air radon test, since soil gas is usually the larger source.
Sources
The facts on this page are drawn from primary public-health and government sources:
By TapWaterData Editorial
Radon in New Hampshire well water FAQ
How common is Radon in New Hampshire private wells?
New Hampshire has a modeled Radon estimate for 10 counties. These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
Is Radon a health risk?
Radon is a health hazard. Inhaling radon released from water is a lung-cancer risk, and there is no national groundwater grid for it — New Hampshire is the only state with a published model. A water radon test, paired with an air test, is the only way to measure your own exposure.
How do I test my New Hampshire well for Radon?
Order a test that covers Radon from a New Hampshire-certified drinking-water lab and compare the result to the EPA limit. The county-level estimate above is an area model for New Hampshire, not a measurement of your individual well — only testing your own water reveals its Radon level.
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