Certified labs by state
California
California private domestic wells are generally the owner’s responsibility, and the State Water Resources Control Board’s GAMA program is the main official source for well-owner testing guidance. California also now maintains an AB 2454 domestic-well testing page and program directory for free state- or regional-board-funded testing opportunities in covered areas. ([waterboards.ca.gov](https://www.waterboards.ca.gov/water_issues/programs/gama/well_owners.html))
Checked against official sources on October 4, 2026. Rules and links change; confirm with the office listed before you act.
- Certifies drinking water labs
- California State Water Resources Control Board, Environmental Laboratory Accreditation Program (ELAP)
- Official certified lab list
- Official page →
- Free or low-cost testing
- California’s AB 2454 page says there are currently 11 domestic-well programs funded or regulated by the State Water Board and/or Regional Water Board, and the county-based assistance page lists programs offering services such as well testing, bottled water, treatment devices, or repair in some areas. ([waterboards.ca.gov](https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/private-domestic-well-testing.html))
Official resources in California
Official State Water Board page for California’s accredited environmental laboratories and ELAP program details. ([waterboards.ca.gov](https://waterboards.ca.gov/drinking_water/certlic/labs/))
Interactive map residents can use to find ELAP-accredited drinking-water laboratories by area. ([waterboards.ca.gov](https://waterboards.ca.gov/drinking_water/certlic/labs/))
California’s official private-well guide with recommended tests, testing frequency, interpretation tips, and protection steps. ([waterboards.ca.gov](https://www.waterboards.ca.gov/water_issues/programs/gama/docs/wellowner_guide.pdf))
Explains who must use free testing programs in covered areas and links to the Well Testing Program Directory and map. ([waterboards.ca.gov](https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/private-domestic-well-testing.html))
Lists current assistance programs by county and the services offered, such as well testing, bottled water, or treatment devices. ([waterboards.ca.gov](https://www.waterboards.ca.gov/water_issues/programs/grants_loans/drinking_water_well.html))
Key facts for California
- California’s certifier is ELAP within the State Water Resources Control Board. ([waterboards.ca.gov](https://waterboards.ca.gov/drinking_water/certlic/labs/))
- California recommends annual testing for total coliform bacteria, nitrate, and electrical conductivity. ([water.waterboards.ca.gov](https://water.waterboards.ca.gov/water_issues/programs/gama/docs/wellowner_guide.pdf))
- California recommends broader minerals testing, including arsenic, every 5–10 years or after taste, odor, color, EC, or land-use changes. ([water.waterboards.ca.gov](https://water.waterboards.ca.gov/water_issues/programs/gama/docs/wellowner_guide.pdf))
- Nitrate-contaminated groundwater is a particularly significant concern in the Tulare Lake Basin and Salinas Valley. ([water.waterboards.ca.gov](https://water.waterboards.ca.gov/water_issues/programs/nitrate_project/?utm_source=openai))
- The GAMA Domestic Well Project is on hiatus pending funding. ([waterboards.ca.gov](https://www.waterboards.ca.gov/water_issues/programs/gama/domestic_well.html?utm_source=openai))
- California says radon in water has no current federal or state drinking-water standard in California; concerned private-well users should test air and water. ([cdph.ca.gov](https://www.cdph.ca.gov/Programs/CEH/DRSEM/Pages/EMB/Radon/Radon-in-Water.aspx?utm_source=openai))
What to do next
- Use the ELAP GIS search to choose a nearby accredited lab before sampling, and ask that lab for bottles, preservation instructions, and turnaround times. ([waterboards.ca.gov](https://waterboards.ca.gov/drinking_water/certlic/labs/))
- Start with annual coliform, nitrate, and EC, then add minerals, VOCs, or radionuclides if local conditions, nearby land uses, or water changes suggest risk. ([water.waterboards.ca.gov](https://water.waterboards.ca.gov/water_issues/programs/gama/docs/wellowner_guide.pdf))
- Check the AB 2454 page and county assistance page for free testing or replacement-water programs in your area before paying privately. ([waterboards.ca.gov](https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/private-domestic-well-testing.html))
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