Most radon coverage stops at the soil beneath your foundation. But Iowa faces a second, quieter exposure path: radon dissolved in private-well water that off-gasses into household air every time someone showers or runs the laundry. When you combine the nation's highest indoor-radon geology with the hundreds of thousands of private wells across rural Iowa, you get a double exposure that generic national guides simply don't address.
Is There Radon in Iowa Well Water?
Yes — radon can occur in Iowa private-well water, and the risk is amplified by Iowa's geology. The same uranium-bearing glacial till and fractured Driftless-area limestone that give Iowa the highest modeled indoor radon in the U.S. (EPA, ~8.5 pCi/L statewide average) can also release radon into groundwater. Private wells that draw from this bedrock can carry that radon directly into the home.
Is It Normal to Have Radon in Well Water?
Radon in well water is common, especially where bedrock contains uranium — which describes much of Iowa. Groundwater moving through uranium-bearing rock dissolves radon and carries it to the wellhead. Public water systems are tested and treated, but private wells are not. The U.S. EPA's Safe Drinking Water Act does not regulate private wells, so testing is the homeowner's responsibility. If you draw from a private well in Iowa, some level of waterborne radon is entirely plausible and worth measuring.
This is distinct from — but related to — the airborne radon that drives most of radon's health risks. The geology that makes Iowa's soil gas so potent is explained in our guide to why Iowa has the highest indoor radon in the country.
How Much of My Radon Risk Comes From Water?
For most homes, water is a small slice of the total radon picture. According to the EPA, only about 1–2% of airborne indoor radon comes from water — the overwhelming majority is soil gas entering through the foundation. That ratio matters for Iowa homeowners: testing your indoor air remains the first priority, and water testing is the targeted follow-up for private-well households.
That said, waterborne radon is not trivial. The EPA estimates radon in drinking water causes roughly 168 cancer deaths per year in the United States. It is a real, measurable hazard — just one that sits behind soil-gas radon in scale.
Is It Safe to Shower in Water With Radon?
The greater risk from radon in water is inhalation, not ingestion. When water containing radon is agitated — during showering, laundry, and dishwashing — the gas escapes into household air, where you breathe it in. According to EPA estimates based on a National Academy of Sciences report, about 89% of the cancer risk from radon in water comes from inhaling this released gas (lung cancer), and only about 11% comes from drinking it (stomach cancer).
So a short, isolated shower is not the concern. The concern is the cumulative airborne radon that waterborne sources add to a home day after day — particularly in a state where the baseline indoor air already runs high.
How Do You Treat Radon in Well Water?
Waterborne radon is treated at the point of entry — where water enters the home — so that every tap, shower, and appliance is covered. The EPA identifies two effective point-of-entry methods: granular activated carbon (GAC) filtration and aeration. Both treat the whole house; neither is a faucet-mounted filter.
| Method | How It Works | Typical Removal | Best For / Trade-offs |
|---|---|---|---|
| GAC (Granular Activated Carbon) | Water passes through a carbon bed; radon adsorbs onto the carbon. | ~90–99% | Lower upfront cost. Radioactivity can collect on the carbon, so the spent filter may require special handling and disposal. |
| Aeration | Air is bubbled through the water to strip out radon, which is vented outdoors by an exhaust fan. | ~95–99% | Generally preferred for high concentrations. Higher upfront and maintenance cost, but no radioactive media to dispose of. |
In short: GAC is often the more economical choice at moderate radon levels, while aeration is typically favored when concentrations are very high. A water-treatment professional should size the system to your tested well-water level in pCi/L.
Is There a Legal Limit for Radon in Iowa Well Water?
There is no federal enforceable standard for radon in drinking water. The EPA has proposed limits for public water systems over the years, but none apply to private wells, and Iowa does not set a binding private-well water-radon limit. As guidance only, some states act on elevated waterborne radon — Wisconsin's DNR, for example, references roughly 4,000 pCi/L in water as a level warranting attention. Treat any such figure as out-of-state guidance, not Iowa law. The practical takeaway for Iowa homeowners: regulation won't catch this for you, so testing is the only way to know.
How Much Does It Cost to Mitigate Radon in Well Water?
Whole-house waterborne-radon treatment generally runs from a few hundred to a few thousand dollars, with national figures commonly cited in the range of about $700 to $4,000 installed. GAC systems tend to sit at the lower end; aeration systems, with their fans and venting, tend toward the higher end. Actual cost depends on your water-radon level, flow rate, and household size — so price the job only after a water test gives you a number in pCi/L.
How Do I Test My Iowa Well for Radon?
Radon-in-water testing uses a specific water sample collected to avoid releasing the gas before analysis — it is not the same as an indoor air test. Iowa homeowners have local help: through Iowa HHS and county public health offices, Iowa's Grants to Counties program supports private-well water testing across the state, and many county offices assist residents with sampling. Start by testing your indoor air (the larger exposure), and if you rely on a private well, add a water-radon test to complete the picture.
Frequently Asked Questions
Does my city water in Iowa have radon?
Municipal systems are tested and treated, so radon in public water is far less of a homeowner concern. This guide is primarily for the many rural Iowa households on private wells, which are not covered by the EPA's Safe Drinking Water Act.
If my air radon is high, does that mean my water has radon too?
Not necessarily. They are separate sources. High indoor air radon usually points to soil gas, which accounts for roughly 98–99% of airborne radon per the EPA. The only way to know your water's level is a dedicated water test.
Will a radon air mitigation system fix radon in my water?
No. A standard sub-slab air system addresses soil-gas radon. Waterborne radon requires separate point-of-entry treatment — a GAC filter or an aeration unit — installed on the water line.
What radon-in-water level should prompt treatment?
There is no Iowa legal threshold. Because the main risk is the radon that off-gasses into your air, decisions are usually guided by your home's overall airborne radon and the water test result together. A qualified contractor can interpret your pCi/L numbers and recommend whether treatment is warranted.