Radon in Washington well water
In Washington, radon was detected in 96% of 702 tested private well samples.
Radon is a radioactive gas released from bedrock into well water. It escapes into household air during showers and washing, where inhaling it raises lung cancer risk. EPA has no enforceable water MCL; New Hampshire recommends treatment above 2,000 pCi/L, and many states use 4,000 pCi/L.
Check your radon number
Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.
Test your Washington well for radon
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
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Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes radon.
Where to get a well tested for radon in Washington: certified labs, state programs and prices.
By county, from individual samples
Public monitoring samples against the EPA limit; counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Grant | no limit | 73 | 100% | 390 | 1,700 pCi/L |
| Whitman | no limit | 44 | 100% | 505 | 2,340 pCi/L |
| Franklin | no limit | 56 | 100% | 515 | 4,000 pCi/L |
| Thurston | no limit | 62 | 95% | 400 | 660 pCi/L |
| Stevens | no limit | 233 | 94% | 4,093 | 171,527 pCi/L |
| Clark | no limit | 82 | 90% | 320 | 820 pCi/L |
- Spokane Reservation CCD, Stevens County94% detected of 232
- Olympia CCD, Thurston County93% detected of 43
Sources
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. radon counts and shares are listed on each county and town page with their sources.