Washington has free or low-cost well testing. Across the state, the ones worth testing for are radon, manganese, nitrate, uranium and arsenic, plus bacteria every year.
About 715,000 people in Washington get their water from a private well, about 1 in 11 residents.
DOH offers free nitrate and coliform testing to eligible well owners in parts of the Lower Yakima Valley and Western Benton County.
Department of Health (DOH); Department of Ecology for well records and lab accreditation: private well testingThe state's list of labs certified for drinking water. Many sell bottles you pick up or get by mail, and their results count for a home sale or loan.
Labs certified by WashingtonOrder online, fill the bottles at your kitchen tap and get results by email in about a week. Full well tests run about $210 to $220.
Compare kits for WashingtonShare of tested wells over the limit, from lab tests the USGS, EPA and state agencies collected since 2000. Your own well needs its own test.
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
5 counties have a full report with local test results and well depths.
No full report for that county yet. The statewide results above still apply, and so do the three ways to get tested.
| County | People on private wells | Share of residents | Typical well depth |
|---|---|---|---|
| Yakima County | 70,576 | 27% | – |
| Thurston County | 48,744 | 17% | – |
| Mason County | 48,663 | 74% | – |
| Pierce County | 40,397 | 4% | – |
| Spokane County | 32,762 | 6% | – |
| Snohomish County | 32,165 | 4% | – |
| Lewis County | 31,997 | 39% | – |
| Stevens County | 30,499 | 66% | – |
| Benton County | 26,184 | 13% | – |
| Kitsap County | 24,998 | 9% | – |
| Cowlitz County | 24,930 | 23% | – |
| Grant County | 24,576 | 25% | – |
| Whatcom County | 24,475 | 11% | – |
| Okanogan County | 23,565 | 56% | – |
| Kittitas County | 23,351 | 53% | – |
| Clallam County | 17,657 | 23% | – |
| King County | 17,399 | under 1% | – |
| Grays Harbor County | 15,889 | 21% | – |
| Franklin County | 15,502 | 16% | – |
| Pend Oreille County | 12,920 | 96% | – |
| Island County | 12,782 | 15% | – |
| Klickitat County | 12,538 | 55% | – |
| Chelan County | 12,079 | 15% | – |
| Walla Walla County | 11,535 | 18% | – |
| Skagit County | 10,925 | 8% | – |
| San Juan County | 8,646 | 49% | – |
| Whitman County | 7,932 | 17% | – |
| Douglas County | 7,421 | 17% | – |
| Jefferson County | 7,372 | 22% | – |
| Lincoln County | 7,371 | 68% | – |
| Adams County | 6,865 | 33% | – |
| Ferry County | 5,842 | 81% | – |
| Pacific County | 5,379 | 23% | – |
| Skamania County | 5,188 | 43% | – |
| Garfield County | 2,286 | 100% | – |
| Wahkiakum County | 1,615 | 37% | – |
| Columbia County | 1,216 | 31% | – |
| Asotin County | 1,032 | 5% | – |
| Clark County | 0 | 0% | – |
Washington doesn't require routine testing of existing private wells. Keeping a well safe is up to the owner, so test for bacteria and nitrate every year.
DOH offers free nitrate and coliform testing to eligible well owners in parts of the Lower Yakima Valley and Western Benton County. Otherwise, use a lab certified by Washington for drinking water. The state's list is linked on this page.