Last checked: October 22, 2026

Certified drinking water labs and licensed well drillers in California

California accredits drinking water labs through the State Water Board's Environmental Laboratory Accreditation Program (ELAP), and licenses well drilling contractors through the Contractors State License Board (CSLB). This list shows the commercial labs on ELAP's accredited drinking water lab data, grouped by county. Filter by county or search by name or town.

How California handles labs and well drillers

• Labs: ELAP accredits labs that analyze drinking water and publishes a map of accredited laboratories.¹ The State Water Board's guide for well owners says it keeps a list of certified drinking water labs, recommends getting quotes before choosing a lab, and says it isn't always required to use a certified lab for a private well.²
• Well drillers: domestic wells must be drilled by a contractor with a C-57 Well Drilling license, and the driller needs a permit from the local permitting agency (usually the county environmental health department) before working on a well.²
• Well records: drillers record a well completion report that goes to the local permitting agency, the Department of Water Resources (DWR) and the well owner.²

Check a license or lab yourself

• C-57 well drilling contractors: CSLB's Instant License Check shows a license's status. CSLB's Public Data Portal offers a free download of licensed contractors by classification and county (choose C-57).³ We couldn't download that list automatically, so it isn't loaded here yet. Well drillers: lookup only.
• Labs: confirm a lab's accreditation and the tests it's accredited for on ELAP's lab map, and call the lab before you send a sample.¹

The list

This list includes the labs ELAP's map data marks as commercial and located in California. It leaves out city, utility, wastewater, industrial and other in-house labs, which usually test only their own samples. County is the county that contains the lab's location on ELAP's map (we matched each map point to a county with the U.S. Census Geocoder).⁴ Labs can test samples from anywhere, and many provide sample bottles by mail, so a lab outside your county may still work for you.

Sources for this list

• California State Water Board, Environmental Laboratory Accreditation Program (ELAP): accredited drinking water laboratories (GIS layer behind ELAP's lab map; commercial labs in California only) (downloaded 2026-10-22): 133 entries

Home inspectors and well inspections

A standard home inspection usually doesn't include a full check of the well. If you're buying or selling a home with a well, ask the home inspector whether they do a well flow (yield) test and water sampling, which state-certified lab runs the samples, and whether they look at the well cap, pressure tank and pump controls. Otherwise, hire a licensed well contractor for the well itself and a certified lab for the water. Are you a home inspector? See our well inspection guide for home inspectors.

NGWA (the National Ground Water Association, a private trade group) recommends a yearly well checkup by a qualified water well professional: a flow test, checks of the water level, pump, pressure tank and switch, a sanitary and code check, a coliform bacteria and nitrate test (plus anything of local concern), and a written report.⁶ To find one, use NGWA's contractor lookup on wellowner.org and its certified professionals directory. These are run by a trade association, not a state agency, so still check the state license.

Where a state publishes its home inspector license list, we load it on that state's page (currently North Carolina and New York). Other states we cover: Texas licenses inspectors through the Texas Real Estate Commission, but TREC's public data file doesn't include a location, so use TREC's license holder search. Wisconsin credentials home inspectors through DSPS, which sells its list rather than publishing it, so use DSPS's credential search. Pennsylvania and Michigan don't have a state license list for home inspectors that we could use.

Water treatment dealers

We list water treatment dealers (softener, filter and treatment system installers) only where a state publishes an official license list. A few states license this work. Where a state publishes its license list we load it (so far Texas: TCEQ Water Treatment Specialists), and where we've found a state license without a usable list, it's noted on that state's page, so check with your state too. To find someone with a voluntary credential, use these lookups. They are run by private trade associations, not by any government agency. A listing there is not a state license, and these groups mostly list their own members:

• Water Quality Association (WQA): Find a WQA-certified professional (people who hold WQA's voluntary certifications) and find WQA-certified treatment products (products WQA has tested and certified).
• National Ground Water Association (NGWA): Find a water well contractor on NGWA's wellowner.org (NGWA members; NGWA says it "neither endorses nor guarantees the work of any company listed")⁷ and the directory of NGWA-certified professionals.

Before you buy treatment, get your water tested by a state-certified lab (each state page lists or links them) and run the results through the free Well Test Results Checker, so you only treat for what's actually in your water.

Questions to ask before hiring a well contractor

Get information on several contractors before you choose.⁸ These questions come from the National Ground Water Association's well owner guidance and New York DEC's consumer checklist:⁸⁹

• Are you licensed, registered or certified by the state for this work? Not every state requires it. Check the answer yourself with the state lookup on this page.
• Is the person supervising the job certified? NGWA offers voluntary certification; its highest level is Master Groundwater Contractor (MGWC).⁸
• Do you file a well log or completion report, and will I get a copy? Some states require the driller to give the owner a copy (New York does, for example).⁹ Keep it with your deed.⁸
• What liability and workers' compensation insurance do you carry?⁸
• Can I talk to recent customers? Ask for references and call them.⁹
• Will you give me a written contract?⁸ In New York, for example, home improvement work over $500 needs a written contract by law.⁹
• Do I need a local permit? Check with your local health and building code officials. Some counties set their own rules.⁹

What to check on a quote

Get more than one estimate.⁹ NGWA says an itemized list of charges is better than a lump sum, because you can't compare offers unless you know what each one covers.⁸ For a drilled well, look for:⁸

• Price per foot of drilling and per foot of casing, plus the casing diameter and thickness
• Other materials (drive shoe, grout, well cap) and other steps (grouting, development, test pumping, disinfection)
• The type of well cap or seal, and the disinfection procedure
• What happens, and what it costs, if they must drill deeper or drill a second well, or abandon and seal a dry or bad hole
• Cleanup of the site, an expected start date, and a guarantee of materials and workmanship
• A statement that the work will meet state and local codes
• What is not included

When the well is finished, NGWA suggests checking the depth against the construction report, asking what yield (gallons per minute) the well was tested at, making sure the cap is secure and at least 6 inches above ground, asking whether the well was disinfected, and getting your copy of the well record.⁸

Buying treatment? Test first. A lab report from a state-certified lab tells you what you're actually treating for. Pennsylvania DEP, for example, says to pick a treatment device for the specific contaminant your test found, and points to NSF's product database.¹⁰ Put your numbers into our free Well Test Results Checker to see how they compare with EPA benchmarks.

More for California well owners

• Private well testing in California: rules, free testing programs, contaminants and county pages
• Well Test Results Checker