A radon water testing measures the amount of dissolved radon gas in your well water using a sealed sample vial and a certified lab. If you get your water from a private well anywhere in the Milwaukee area, this is the only way to know whether your water supply is adding to your home’s indoor radon level. Results usually arrive within a week and tell you whether treatment is worth considering.
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How Radon Gets Into Well Water
Radon forms when uranium and radium in rock and soil break down. As groundwater moves through bedrock, some of that radon dissolves into it. Wisconsin DNR data shows the highest dissolved radon concentrations turn up in wells drawing from granite or granitic sand-and-gravel formations, mostly in north-central and northwestern Wisconsin.
The city of Milwaukee itself draws municipal water from Lake Michigan, a surface source, so most of its radon has already escaped to the atmosphere before the water reaches your tap.
But a large share of the suburbs Milwaukee Radon Home serves, including much of Waukesha County, rely on private wells. Waukesha County alone has more than 40,000 private wells, and per Wisconsin DNR, every well in the state carries some level of dissolved radon. Testing is the only way to find out your number.
A separate but often-confused issue is radium contamination in Waukesha County’s deep sandstone aquifer, driven by decades of over pumping.
Radium and radon are both naturally occurring radioactive elements from the same decay chain, but they’re different contaminants with different health risks and different treatment methods. A radon water test doesn’t tell you your radium level, and vice versa.
Why a Radon Water Test Matters for Your Health
Radon dissolved in water is far more dangerous once it escapes into the air than when it’s swallowed. Showering, running the dishwasher, and doing laundry all release dissolved radon into your home’s air, where you breathe it in. Drinking the water carries a smaller stomach-cancer risk from ingestion.
The EPA estimates radon exposure overall, mostly from soil gas seeping through foundations, causes about 21,000 lung cancer deaths per year in the United States, making it the second-leading cause of lung cancer after smoking.
Radon in drinking water is a smaller slice of that total: EPA estimates it contributes to roughly 168 deaths per year nationally, with about 89 percent of those from lung cancer caused by inhaling radon released from water during everyday use, and the rest from ingestion.
Wisconsin DHS puts a number on the water-to-air relationship: at 10,000 pCi/L in your water supply, the lifetime inhalation risk works out to roughly 2 in 1,000 for people who have never smoked and about 9 in 1,000 for smokers. The lifetime ingestion risk at that same level, mostly stomach cancer, is about 7 in 10,000.
Is Radon in Well Water a Real Concern in the Milwaukee Area?
Somewhat reassuring news first: Wisconsin DHS sampled more than 500 private wells across the state in a grid pattern, and none south of a line running roughly from La Crosse to Green Bay tested above 5,000 pCi/L. That line covers the entire Milwaukee metro.
That’s an average, not a guarantee. Individual wells vary a lot depending on the specific bedrock they draw from, even within the same neighborhood. The only way to know your own well’s number is to test it.
When Should You Test Your Well Water for Radon?
A few situations make water testing worth doing sooner rather than later:
- You’re on a private well and have never tested it for radon. Wisconsin doesn’t require it, and the federal Safe Drinking Water Act’s radon rules don’t apply to individual wells, so the responsibility falls on you as the homeowner.
- Your indoor air radon test came back at or above the EPA’s action level of 4 pCi/L and you’re on a private well.
- You just drilled a new well, or added a second well on the property.
- You’re buying or selling a home served by a private well. Wisconsin doesn’t require radon testing in real estate transactions, but it’s recommended.
- You’re planning a radon-resistant new construction build and want the water source accounted for alongside the soil-gas plan.
How to Test Well Water for Radon: Step by Step
A DIY kit is straightforward, but the collection method matters more than people expect. Radon escapes from disturbed or exposed water quickly, so a rushed or sloppy sample skews the result.
- Order a certified radon-in-water test kit. Wisconsin residents can get one through a Wisconsin Radon Information Center or the Wisconsin State Laboratory of Hygiene, or through a national certified lab.
- Run the cold tap for a couple of minutes before sampling, to clear out standing water sitting in the line.
- Fill the kit’s small glass vial carefully, without splashing. Avoid letting the sample sit open to air, even briefly, since that’s when radon escapes and skews the reading.
- Seal the vial immediately and return it to the lab the same day, following the kit’s specific instructions.
- The lab analyzes the sample using liquid scintillation counting. Most results are ready within about a week of the lab receiving your sample.
DIY Kits vs. Professional Water Radon Testing
Both routes use the same underlying lab science. The difference is who collects the sample and how fast you need an answer.
| Method | Typical Cost | Turnaround | Best For |
| Mail-in DIY kit | $25–$130* | About 1 week | Routine screening for most homeowners |
| State lab program | $25–$60* | About 1 week | Budget testing through the Wisconsin State Laboratory of Hygiene |
| Professional on-site sampling | Varies by provider* | Days to about 2 weeks | New construction, real estate deals, complex plumbing |
How to Read Your Radon Water Test Results
There’s no legally enforceable federal limit for radon in drinking water yet. The EPA proposed one in 1999, either 300 pCi/L as a default limit or 4,000 pCi/L for states with an approved indoor-air radon program, but Congress never finalized it, and that status hasn’t changed since.
Wisconsin DNR’s practical guidance: consider modifying your water supply if your well tests above 4,000 pCi/L. Below that, most homes don’t need water-specific treatment.
For scale, Wisconsin DHS estimates that every 10,000 pCi/L of radon in your water adds roughly 1 pCi/L to your indoor air on average. A well testing at 4,000 pCi/L would be expected to add well under half a pCi/L to your home’s air, on its own well below the EPA’s air action level of 4 pCi/L.
That’s why water testing works best paired with an indoor air test rather than instead of one. Soil gas seeping through your foundation is almost always the bigger contributor. See our guide to radon testing devices for how to test the air side.
What to Do If Your Well Water Radon Is High
Two methods are the industry standard for treating radon in water. A third option people often ask about doesn’t actually work for radon.
- Granular activated carbon (GAC) filtration adsorbs radon as water passes through a bed of activated carbon. It’s typically the lower-cost option. One caveat from Wisconsin DNR: at high radon levels (4,000 pCi/L and up), spent GAC filters can accumulate enough radioactivity that they need careful handling and disposal.
- Aeration systems strip radon out of the water by exposing it to air before it enters your plumbing, then vent that air outdoors. These cost more upfront but avoid the filter-disposal issue.
- Reverse osmosis does not remove radon. RO membranes are built to block dissolved solids like arsenic, radium, and lead. Radon is a dissolved gas, and gas molecules pass straight through an RO membrane. If radon is your specific concern, GAC or aeration are the methods that actually work.
Wisconsin DNR requires any aeration or GAC system to be approved by the state’s Department of Safety and Professional Services plumbing program, and recommends a consultation with the DNR’s Bureau of Drinking Water and Groundwater before installation.
Per Wisconsin DHS, single-house radon water removal systems typically run $3,000 to $5,000 to install and operate over about 10 years. For whole-home soil-gas systems rather than water-specific treatment, see our guide to types of radon mitigation systems.
Radon Water Testing Cost in Milwaukee
A full picture: testing runs $25 to $130 depending on the kit and lab, and treatment (if your well needs it) runs $3,000 to $5,000 for a GAC or aeration installation. That’s separate from indoor air radon testing and mitigation costs, which are usually lower and covered in our radon testing cost guide.
Frequently Asked Questions
Does a radon water test replace an indoor air radon test?
No. They measure two different things. Water testing tells you whether your well is adding to your indoor radon. Air testing tells you your home’s actual radon level, which is what matters for your health and for the EPA’s action level. Most homes need both, especially on a private well.
Can boiling water get rid of radon before I drink or cook with it?
Boiling releases dissolved radon into the air rather than removing it safely, so it isn’t a real treatment method. It can actually raise the radon level in your kitchen air temporarily. Use GAC filtration or aeration instead if your well tests high.
Is Milwaukee’s city water at risk for radon?
City of Milwaukee water comes from Lake Michigan, a surface source, and most dissolved radon escapes before it reaches your tap. Treatment is rarely necessary for city water customers. If you’re anywhere in the metro on a private well, testing is still the only way to know your number.
How often should I retest my well water for radon?
Radon levels in a well can shift over time with drought, seismic activity, or new drilling nearby. Retesting every several years, or any time your well changes (new pump, new well, noticeable change in water), is a reasonable practice.
My water test is high but my indoor air test is low. What’s going on?
That can happen when water use is low relative to the size of the home, or when ventilation carries the released radon away before it accumulates. It’s still worth addressing the water number per Wisconsin DNR’s 4,000 pCi/L guidance, since it adds to your baseline exposure over time even if today’s air reading looks fine.
Conclusion
Radon in well water may be invisible, but its health impact is tangible. Homeowners with private wells, older homes, or families planning new construction must incorporate radon water testing into their safety plans.
If you’re on a private well anywhere in the Milwaukee area, water and air radon testing take the guesswork out of an invisible problem. Schedule a radon inspection with Milwaukee Radon Home, and we’ll walk you through both.
By following the step‑by‑step guide, reviewing good cost estimates, and understanding the special features that qualify a home as radon resistant new construction, you gain peace of mind that your indoor air remains healthy.
If you want a professional assessment or would like a quote for a radon‑removal setup, contact us today. We will send a free on‑site evaluation, walk you through the sample procedure, and provide a price that keeps your home safe without breaking the bank.
