Well Water Notebook
Information only, not medical advice. We never say whether your water is safe to drink. Ask a state-certified lab or your local health department. Disclaimer

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Well water testing in Fresno County, California

Fresno County had more people on their own household wells than any other California county in USGS's 2015 estimates. Here's who permits wells, where to get free testing, what to test for and where to find a lab or a licensed driller, with a source for every fact.

This page can't tell you whether your water is safe to drink. Only a test of your well can do that.

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How many people here use a private well

USGS estimates that about 102,000 people in Fresno County supplied their own household water in 2015, about 10% of the county's population, the most of any California county.1

Who regulates wells in Fresno County

The State of California doesn't regulate water quality in private domestic wells.2 Fresno County says plainly: "Private wells are not required to meet any water quality standards."3

The Fresno County Department of Public Health, Environmental Health Division issues well permits in the unincorporated county; for wells inside an incorporated city, contact the city. The county says:3

Groundwater use is regulated by local Groundwater Sustainability Agencies (GSAs), not the county's well permit program. Fresno County says the critically overdrafted subbasins must reach sustainability by 2040 and tells owners to check with their GSA.3 See SGMA on the California page.

Free well testing in Fresno County

The State Water Board's Well Testing Program Directory (June 2026) lists these programs for Fresno County.4 Check that your address is in the service area before you apply.

Program Area served Replacement water offered?
Community Water Center Fresno County No
Kings Water Alliance Fresno County Yes
Self-Help Enterprises (559-802-1289) Fresno County Yes
Valley Water Collaborative Delta-Mendota groundwater basin Yes

If you rent out a home on a domestic well inside one of these program areas, California's AB 2454 requires you to test through the program and share results with tenants within 10 days.5 See renting out a home on a well.

What to test and how often

The State Water Board recommends testing total coliform bacteria, nitrate and electrical conductivity every year, plus a mineral panel every 5 to 10 years.2 In the Board's 2007–2017 public supply well data, Fresno County had the second-most public wells with 1,2,3-TCP above California's limit of 0.005 µg/L.67 That's public well data, not a survey of private wells, but it's a reason to ask a lab about adding 1,2,3-TCP. See the California contaminant table.

Buying a home with a well in Fresno County

California's Transfer Disclosure Statement asks the seller whether the water supply is a well, but we didn't find a statewide rule requiring a well test at sale.8 Ask for the well completion report (DWR's Well Completion Report Map Application), a water test and a flow test. See buying a home with a well.

Get quotes from local well pros

Need a well drilled, a pump fixed, your water tested or treated, or a well inspected for a home sale in Fresno County, California? Tell us what you need. With your permission, we'll try to pass your request to up to 3 local licensed or certified providers. It's free. You can also look up licensed pros yourself in our directory.

Well Water Notebook is a free information site, not a contractor, and we can't guarantee anyone will contact you. We don't sell your details or add you to a mailing list. See our privacy policy.

Where to get tested and treatment options

Labs: see accredited labs in Fresno County, from the State Water Board's ELAP data. Confirm with the lab that it's accredited for each test you need.9

Drillers: check a C-57 license with CSLB's Instant License Check.

Dry well? Report it on DWR's Dry Well Reporting System.10

If a result is high:

  1. Dieter, C.A., and others, 2018, Estimated Use of Water in the United States County-Level Data for 2015 (ver. 2.0), U.S. Geological Survey data release. https://doi.org/10.5066/F7TB15V5 ↩

  2. California State Water Resources Control Board, GAMA Program, A Guide for Private Domestic Well Owners (June 2025). https://www.waterboards.ca.gov/water_issues/programs/gama/docs/wellowner_guide.pdf ↩↩

  3. County of Fresno, Department of Public Health, Environmental Health Division, "Well Permitting Program." https://www.fresnocountyca.gov/Departments/Public-Health/Environmental-Health/Water-Surveillance-Program/Well-Permitting-Program ↩↩↩

  4. California State Water Resources Control Board, Well Testing Program Directory (spreadsheet, last updated June 2026). https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/docs/well-testing-program-directory.xlsx ↩

  5. California State Water Resources Control Board, "Rental Property Domestic Well Testing Requirements (AB 2454)." https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/private-domestic-well-testing.html ↩

  6. California State Water Resources Control Board, GAMA, "1,2,3-Trichloropropane (TCP)" fact sheet (public supply well data, 2007–2017). https://www.waterboards.ca.gov/water_issues/programs/gama/docs/coc_tcp123.pdf ↩

  7. California State Water Resources Control Board, "MCLs, DLRs, and PHGs for Regulated Drinking Water Contaminants" (updated September 2025). https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/mclreview/mcls_dlrs_phgs.pdf ↩

  8. California Department of Real Estate, Disclosures in Real Property Transactions (RE 6). https://www.dre.ca.gov/files/pdf/re6.pdf ↩

  9. California State Water Resources Control Board, "Environmental Laboratory Accreditation Program (ELAP)." https://www.waterboards.ca.gov/drinking_water/certlic/labs/ ↩

  10. California Department of Water Resources, "Dry Well Reporting System." https://mydrywell.water.ca.gov/report/ ↩