Radon has turned up often in 1 of the 5 Washington counties with 10 or more tested wells, but those results likely overstate it, because of who tested the wells, when or where. 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.
Across Washington, about 2 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (27 of 137). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Washington wells about 5 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.
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 |
|---|---|---|---|
| Stevens County | 61 | Widespread | |
| Kitsap County | 18 | Rare | |
| Grant County | 12 | Rare | |
| Franklin County | 10 | Rare | |
| Whitman County | 10 | Rare |
* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:
12 more Washington counties have 1 to 9 tested wells for radon in water, too few to rate.
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Free nitrate and bacteria testing in Washington is limited to parts of the Lower Yakima Valley and western Benton County. Check which tests it includes before you count on it for radon in water.
Washington's private well pageAsk for radon in water by name. Results from a certified lab count for a home sale or a loan.
Labs certified by WashingtonFill the bottles at your kitchen tap and mail them back. We mark the kits that include radon in water.
Compare kitsRadon has turned up often in 1 of the 5 Washington counties with 10 or more tested wells, but those results likely overstate it, because of who tested the wells, when or where. Across Washington, about 2 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (27 of 137). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Washington wells about 5 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.
Free nitrate and bacteria testing in Washington is limited to parts of the Lower Yakima Valley and western Benton County. If that doesn't cover you, use a lab certified by Washington for drinking water, or a mail-in kit that includes radon in water from a certified lab.
See Washington's list of certified labs, or compare mail-in kits.