Radon in Water: What Homeowners Need to Know
Most radon conversations focus on the gas seeping up through the soil, but radon can also dissolve into groundwater and ride into your home through the plumbing. Radon in water mainly concerns private well owners, and the gas escapes into household air during everyday activities like showering and laundry. It is usually a smaller contributor than soil gas, but it is worth understanding. This guide summarizes EPA and CDPHE guidance current as of 2026 for Front Range homeowners. It is educational only; consult a certified radon or water professional for testing and a physician about any health concerns.
What Is Radon in Water?
Radon in water is dissolved radon gas that has entered groundwater from the surrounding rock and soil. As water moves through uranium-bearing formations underground, radon produced by natural decay dissolves into it the same way carbon dioxide dissolves into a sealed soda. When that water reaches a home and is agitated, by a showerhead, faucet, or washing machine, the dissolved radon is released into the indoor air, just as opening a soda releases its fizz.
Two exposure routes exist. The larger one is inhalation: radon escaping from water into the air you breathe throughout the house. The smaller one is ingestion: drinking water that still contains dissolved radon. For most households, the airborne portion is the greater concern, which ties waterborne radon back to the same lung-health issue covered across our pillar on radon testing in Colorado.
Who Is Most at Risk?
Radon in water is overwhelmingly a private-well issue. Homes on private wells draw water directly from groundwater, so any dissolved radon arrives with it straight from the aquifer. Municipal water systems, by contrast, typically store and treat water in open tanks and processes that allow much of the radon to escape before it reaches your tap, so public-supply homes rarely have a significant waterborne radon problem.
If you are on the Front Range and rely on a private well, especially in areas with uranium-rich geology, radon in water is worth checking alongside your air test. The same geology that produces high soil-gas radon in this region can produce radon-rich groundwater. Understanding the broader picture of where this gas originates helps; see our guide to sources of radon.
How Big a Problem Is It?
For most homes, soil gas entering through the foundation accounts for the large majority of indoor radon, and water is a secondary source. A common rule of thumb the EPA has cited is that roughly 10,000 pCi/L of radon in water contributes about 1 pCi/L to indoor air. So water concentrations have to be quite high to add meaningfully to the air level you breathe.
That said, very high waterborne radon can be a real contributor in some well-supplied homes, and ingestion carries its own smaller risk that regulators have considered separately. The practical takeaway: test your air first, since that is where most of the risk lies, and if you have a private well, test your water too, particularly if your air level is elevated and you want to find and address every source rather than guess.
How to Test for Radon in Water
Testing water for radon requires a specific procedure because radon escapes when water is agitated or exposed to air, which would skew the result low. The basic approach:
- Use a dedicated radon-in-water test kit, separate from an air test
- Collect the sample carefully to avoid agitating or aerating the water
- Follow the kit’s instructions for filling vials with minimal air space
- Send the sample promptly to the designated laboratory, since radon decays quickly
Because the sampling technique matters and the gas is short-lived, careful handling and prompt mailing are essential to a meaningful result. A sample that sloses radon on the way to the lab will understate the true level. If your air test is high, identifying whether water is a contributor helps target treatment. Many well owners begin by confirming their air level with an at-home radon test kit before testing the water, since air is the dominant pathway.
How to Treat Radon in Water
If a water test shows significant radon, two treatment methods are standard, and they work in different ways.
Aeration
Aeration systems bubble air through the water to strip out radon, then vent the released gas safely outdoors before the water reaches your taps. Aeration is generally considered the most effective method and avoids concentrating radioactivity in a filter, which makes maintenance simpler.
Granular Activated Carbon (GAC)
GAC systems pass water through carbon that adsorbs radon. They can be effective for lower concentrations but accumulate radioactivity over time, which requires careful handling and eventual disposal of the spent media. For high radon levels, aeration is often preferred for this reason.
Both are point-of-entry systems that treat all water entering the home, which is preferred over point-of-use because radon exposure happens throughout the house during showers and laundry, not just at the kitchen tap. Treating water addresses only the waterborne portion; if soil gas is also elevated, you will still need air mitigation. Our guide to removing radon from a home covers the air-side fix.
Coordinating Water and Air Mitigation
Because most indoor radon comes from soil gas, the usual sequence is to test and address the air first with an active soil depressurization system, then test the water if a private well is involved and the air level remains a concern after the soil-gas system is running. Treating water alone rarely solves an elevated air reading driven by soil gas, so spending on water treatment first can be money misdirected. A professional can help you sort out which source is contributing and in what proportion, so you invest in the fix that actually moves your numbers rather than guessing.
Signs You Should Test Your Well Water for Radon
Not every well owner needs to rush to test water for radon, but certain signals make it worthwhile. Because waterborne radon is usually secondary to soil gas, the strongest trigger is an elevated air reading in a home that draws from a private well. Other indicators include:
- A private well in a high-radon region such as the Colorado Front Range
- An elevated indoor air radon level that persists after soil-gas mitigation
- Neighbors on private wells who have found radon in their water
- A new well or a change in your water source
If none of these apply and your air test is low, waterborne radon is unlikely to be a meaningful concern for your household. The point is to test where the evidence points rather than testing everything reflexively. For a well owner in a uranium-rich area with an elevated air reading that will not come down, the water is a logical next place to look, and confirming it lets you target treatment precisely.
How Water Treatment Fits the Bigger Picture
Treating radon in water makes sense only as part of a complete approach to a home’s radon, not as a standalone fix. Because the soil beneath the foundation supplies most indoor radon in the typical home, addressing the air through an active soil depressurization system is almost always the first and most impactful step. Water treatment comes into play when a private well is a confirmed contributor and the air system alone has not brought levels low enough.
Sequencing the work this way avoids wasted spending. Installing an aeration system to strip radon from water will do little for an air problem driven by soil gas seeping through foundation cracks. A professional who measures both pathways can tell you what share of your indoor radon each source contributes and recommend the combination that brings your home to a safe level. For most Front Range well owners, that means a soil-gas system first, with water treatment added only if the numbers show it is needed. Coordinating the two ensures every dollar goes toward the source that is actually raising your exposure.
When to Call a Professional
Call a certified radon professional if you have a private well and an elevated air radon reading, if your water test shows high radon, or if you are unsure whether water or soil gas is the main contributor. A qualified provider can test both pathways, recommend aeration or GAC treatment for water, and coordinate air mitigation if needed. For Front Range well owners, checking both sources gives the most complete protection, and a professional ensures the two systems work together rather than at cross purposes. The reassuring part is that both waterborne and soil-gas radon have well-established, effective fixes, so even a home with elevated radon from both sources can be brought to a safe level with the right combination of treatments. The key is measuring before you spend, so that each dollar addresses a source that is genuinely contributing to your exposure.
How Radon Escapes From Water Into the Air
Understanding the mechanism makes the risk easier to grasp. Radon stays dissolved in water as long as the water is still and under pressure, much like the gas in an unopened bottle of soda. The moment the water is agitated or exposed to air, the radon comes out of solution and into the surrounding air. In a home, that release happens most strongly during activities that spray, splash, or heat water.
The biggest contributors are usually showers, where hot water is broken into fine droplets in an enclosed space, followed by dishwashers, washing machines, and running faucets. Because bathrooms and laundry areas are often small and less ventilated, radon released there can briefly reach higher concentrations before it disperses through the home. This is why waterborne radon is fundamentally an inhalation concern: the gas you breathe while showering matters more than the small amount you might swallow by drinking. It also explains why point-of-entry treatment, which removes radon from all the water before it reaches any fixture, is preferred over a single under-sink filter that would leave showers and laundry untreated.
Radon in Water Versus Other Water Contaminants
Well owners juggling several water-quality concerns sometimes wonder how radon fits among them. Unlike bacteria, nitrates, or heavy metals, radon’s primary hazard is not from drinking the water but from breathing the gas it releases into household air. This makes radon in water an air-quality issue dressed up as a water issue, which is why the standard treatments aim to strip the gas before it reaches your taps.
A few distinctions help put it in context:
- Exposure route — radon harms mainly through inhalation, while most other contaminants harm through ingestion
- Detection — radon requires a special sampling procedure, since it escapes when water is agitated
- Treatment — aeration and granular activated carbon target radon specifically
- Priority — for most homes, soil-gas radon outweighs waterborne radon as a source of risk
For a Front Range well owner running a comprehensive water test, adding a radon-in-water test is reasonable, particularly if indoor air radon is elevated. But the result should be weighed against the home’s air radon, since that is usually the dominant contributor. A well that tests positive for radon alongside other issues simply means the treatment plan needs an aeration or carbon stage to address it. Understanding that radon behaves differently from typical water contaminants helps you choose the right treatment rather than assuming a standard filter will handle it.
References
- Radon in Drinking Water — U.S. Environmental Protection Agency
- Radon and Private Wells in Colorado — Colorado Department of Public Health and Environment
- Health Risk of Radon — U.S. Environmental Protection Agency
- Radon and Lung Health — American Lung Association
If you rely on a private well on the Front Range and want both air and water radon checked, contact us here to connect with a vetted local professional.