Certified labs by state
Washington
Washington splits private-well oversight across agencies: the Department of Ecology accredits drinking-water laboratories and regulates well construction, while the Department of Health publishes private-well testing guidance. DOH says about 725,000 Washington residents use individual private wells, and local health jurisdictions regulate many private-well matters.
Checked against official sources on October 4, 2026. Rules and links change; confirm with the office listed before you act.
- Certifies drinking water labs
- Washington State Department of Ecology, Environmental Laboratory Accreditation Program (WA ELAP)
- Official certified lab list
- Official page →
- Free or low-cost testing
- DOH says people within a specific boundary of the Lower Yakima Valley or Western Benton County may qualify for free nitrate and coliform well testing, and nitrate-affected private or Group B wells may also get locally administered reimbursement-based help through the Alternative Drinking Water Program.
Official resources in Washington
Consumer hub with Washington private-well guidance, arsenic and PFAS materials, and links to private-well publications.
State page telling private-well owners what to test, how often, and when free nitrate/coliform testing may be available.
Ecology page for private-well testing that points residents to accredited labs and local health departments.
Official searchable list of Ecology-accredited laboratories, including filters for analytes and labs that accept public samples.
State assistance program for communities and local health partners addressing contamination affecting private and Group B wells.
Key facts for Washington
- DOH Office of Drinking Water says about 725,000 Washington residents get drinking water from individual private wells.
- Ecology and DOH say private-well owners should test every year for coliform bacteria and nitrate.
- DOH Testing Your Water suggests arsenic testing at least twice while you own the well: once in summer and once in winter.
- DOH says many Washington wells have arsenic above 10 ppb; reported results range from 10 ppb to 33,000 ppb.
- DOH radionuclide guidance flags uranium potential in northeastern Washington, especially Spokane, Pend Oreille, Stevens, Ferry, and Okanogan counties.
- DOH says residents in a specific boundary of the Lower Yakima Valley or Western Benton County may qualify for free nitrate and coliform testing.
What to do next
- Use Ecology Lab Search, choose the analyte you need, and select labs that accept public samples before collecting bottles or samples.
- Start with yearly coliform and nitrate, then ask your county health department whether your area also warrants arsenic, uranium, radon, or PFAS testing.
- If you are in the Lower Yakima Valley or western Benton County, check DOH's eligibility form for free nitrate and coliform testing; if contamination is found, ask about ADWP-funded local help.
Helpful guides
- How to choose a state-certified drinking water lab
- What to test your private well water for (and how often)
- How to collect a well water sample without ruining the test
- How to read a water test report: MCLs, units and flags