Free testing, with limits
Montana's free well testing is only for childcare facilities. Check which tests it includes before you count on it for radon in water.
Montana's private well pageRadon in Montana well water, by county
Radon is widespread, over the limit in 15% or more of tested wells, in 2 of the 5 Montana counties with 10 or more tested wells. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.
How Montana compares with the rest of the country
Across Montana, about 2 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (31 of 168). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Montana wells about 4 times as often as in the country as a whole, and a test is worth adding even if your county isn't on the list below.
Why it matters: It escapes into the air when you shower or run the tap, and breathing it raises the risk of lung cancer.
Radon is a gas given off by uranium in granite and similar rock.
Radon in tested wells, county by county
Share of each county's tested wells with at least one result over 4,000 pCi/L, a level the EPA proposed. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.
| County | Wells tested | Wells over the limit | Level |
|---|---|---|---|
| Jefferson County | 66 | Widespread | |
| Silver Bow County | 13 | Widespread | |
| Lewis and Clark County | 21 | Worth checking | |
| Ravalli County | 18 | Rare | |
| Carbon County | 14 | Rare |
8 more Montana counties have 1 to 9 tested wells for radon in water, too few to rate.
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Where to get your well tested for radon in water in Montana
A lab Montana certifies
Ask for radon in water by name. Results from a certified lab count for a home sale or a loan.
Labs certified by MontanaA mail-in kit
Fill the bottles at your kitchen tap and mail them back. We mark the kits that include radon in water.
Compare kitsKeep reading about wells in Montana
- Well water testing in Montana: how to get tested and what turns up statewide
- Radon in well water: where it comes from, what it does and how to remove it
- Nitrate in Montana wells, by county
- Arsenic in Montana wells, by county
- Uranium in Montana wells, by county
- Manganese in Montana wells, by county
- Lead in Montana wells, by county
Questions people ask about radon in water in Montana
Is there radon in water in Montana well water?
Radon is widespread, over the limit in 15% or more of tested wells, in 2 of the 5 Montana counties with 10 or more tested wells. Across Montana, about 2 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (31 of 168). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Montana wells about 4 times as often as in the country as a whole, and a test is worth adding even if your county isn't on the list below.
Where can I get my well tested for radon in water in Montana?
Montana's free well testing is only for childcare facilities. If that doesn't cover you, use a lab certified by Montana for drinking water, or a mail-in kit that includes radon in water from a certified lab.
See Montana's list of certified labs, or compare mail-in kits.
Where these numbers come from
- Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over 4,000 pCi/L, a level the EPA proposed. Wells tested for studies and monitoring, not a random sample of homes.
- Likely overstated: our own check of who tested the wells, when and where. How we check.
- State programs and links: Department of Environmental Quality.