Radon in private well water
Radon is a radioactive gas produced by decaying uranium in bedrock. It dissolves into well water and is released into the air when you shower or run the tap. New Hampshire's granite bedrock makes it a notable private-well concern there.
Is it 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.
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.
How common is Radon in US private wells?
No national grid — New Hampshire-only model
There is no national groundwater model for Radon in private wells. A state-specific model exists only for New Hampshire (covering 10 counties there). Everywhere else, the only way to know your level is to test your own well.
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.
Radon risk by state
States with a modeled Radon estimate for private wells, highest area-risk first. Each links to the county-level detail.
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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 well water FAQ
Is Radon a health risk in private wells?
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 US private wells?
There is no national groundwater grid for Radon in private wells. A state-specific model exists only for New Hampshire; everywhere else, the only way to know your level is to test your own well.
How do I find out if Radon is in my well?
Radon is not something you can see, taste, or smell your way to certainty about. Order a test that covers Radon from a state-certified drinking-water lab, collect the sample exactly as the kit instructs, and compare the result to the EPA limit. County-level area estimates describe a region as a whole and cannot stand in for testing your own well.
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