About this list
- Agency
- California State Water Resources Control Board - Environmental Laboratory Accreditation Program (ELAP)
- Format
- ArcGIS map layer (JSON) + per-lab Fields of Accreditation PDFs, analyte-level
- Homeowner flag
- ELAP's map layer gives each lab a type. Labs of type 'Commercial' take commercial samples; that is broader than 'homeowner', so call before you send a sample. Other lab types (city, water district, wastewater, industrial ...) are not marked either way.
Certified as ofMap layer fetched 2026-11-15; scope PDF as of 6/8/2026
California ELAP - Accredited Laboratories (map layer) + per-lab Fields of Accreditation. Fetched 2026-11-15 (UTC).
Official sourceTesting your well in California
How often to test
- The State Water Board's well-owner guide recommends testing once a year. At a minimum: total coliform bacteria, nitrate and electrical conductivity every year. A minerals panel (arsenic, lead, manganese, iron and other metals) every 5 to 10 years, or sooner if conductivity, taste, color, odor or nearby land use changes. [1]
Free testing
- Free well testing is offered in some areas through domestic well programs funded or regulated by the State Water Board or a Regional Water Board. The Board counts 11 such programs. Services and eligibility differ by program, and some also provide replacement drinking water. [2]
- The Board's Well Testing Program Directory (updated June 2026) lists well testing programs in Fresno, Kern, Kings, Madera, Mariposa, Merced, Monterey, San Benito, San Joaquin, San Luis Obispo, Santa Barbara, Santa Cruz, Stanislaus and Tulare counties, and in parts of Riverside (eastern Coachella Valley), Yolo (Yolo groundwater basin), San Mateo, Santa Clara and Ventura counties. Many cover only a groundwater basin or part of a county, so check the service area. [3]
Testing programs and help
- The state does not regulate water quality in most private domestic wells, but counties or local agencies may have their own rules. For example, some wells on farmland may have to be tested for nitrate. Local environmental health agencies may help you read your results. [1]
State lab and rules
- The State Water Board keeps a list of certified drinking water labs, but its guide says a private well owner does not always have to use one. It suggests getting quotes first and estimates a basic analysis at $100 to $400. [1]
- Rentals: under Assembly Bill 2454 (2024), if a domestic well serves a rental property inside the area of a free testing program funded or regulated by the State Water Board or a Regional Water Board, the owner must test the well through that program and share the results, with guidance on reading them, with tenants within 10 days. If results exceed drinking water standards, the program offers free replacement water, and the owner or the residents meet its eligibility rules, the owner must provide safe drinking water. The owner may not charge tenants, or raise rent or fees, for testing or water. [2]
Show the numbers
| Item | Value | Note |
|---|---|---|
| Zone 1 | 2 counties | |
| Zone 2 | 29 counties | |
| Zone 3 | 27 counties |
Radon in indoor air, not in water. EPA: Zone 1 = highest potential (average indoor radon may be above 4 pCi/L); Zone 2 = 2 to 4; Zone 3 = below 2. EPA says the map should not be used to decide whether an individual home needs testing. Source: U.S. EPA, Map of Radon Zones, county list (EPA 402/A-16/001, spreadsheet Sep 2025), accessed 2026-11-01.
Sources
- California State Water Resources Control Board, GAMA Program, A Guide for Private Domestic Well Owners (June 2025)
- California State Water Resources Control Board, Rental Property Domestic Well Testing Requirements (AB 2454) (page last updated Jun 30, 2026)
- California State Water Resources Control Board, Well Testing Program Directory (spreadsheet, last updated June 2026)
- U.S. EPA, Map of Radon Zones, county list (EPA 402/A-16/001, spreadsheet Sep 2025)
Loan test (FHA, VA, USDA) in California
- VA. Test results are valid for 90 days from the date the local health authority certifies them, unless the local authority says otherwise. VA’s chapter names no list of contaminants: the water must meet the local health authority’s requirements, or EPA guidelines where it has none. Your lender may ask for specific tests.
- FHA. A well test is required in the situations FHA’s handbook lists, among others, and the report may not be more than 180 days old at disbursement.
- USDA. Guaranteed loans need a water quality test for a private well, done by the local health authority or a state-certified lab, and no more than 180 days old at closing.
Lenders can ask for more (extra tests, a particular lab, who takes the sample): ask your lender before you book. Federal rules as read on Nov 3, 2026 source 1 source 2 source 3. Full comparison: VA, FHA and USDA well water test requirements. Loan test kits sold by mail, with price and days to results: kits compared.
What California labs say on their own websites
State lists say what a lab is certified for, not whether it takes your sample or what it costs. We read each lab’s own site; a second reader re-checked every fact below. 90 labs on this list are on our register so far; 22 say they take homeowner samples and 10 print a price.
| Lab | Bacteria (coliform / E. coli) | Nitrate | Arsenic | Lead | Basic well panel | Home sale / loan package | Turnaround |
|---|---|---|---|---|---|---|---|
| Abalone Coast Analytical, Inc. San Luis Obispo, CA · You collect the sample with the lab's bottles | Drinking Water Presence/Absence Coliform Test: $60 + $10 ELAP Fee — Next Day Results source | – | – | – | – | – | Drinking Water Presence/Absence Coliform Test: $60 + $10 ELAP Fee — Next Day Results |
| Caltest Analytical Laboratory Napa, CA · You collect the sample with the lab's bottles | Cost is $61 for 5-7 day turnaround time source Total Coliform and E.Coli by Quanti-tray $85 source | Nitrate $66 source | Arsenic $46 ... Metals preparation fee (per sample) $38 source | Package #3: Lead and Copper (FIRST DRAW). Cost is $125 for 3 week turnaround time source | Package #2 ... Cost is $445 for 3 week turnaround time source | – | Package #1: 5-7 day turnaround time. Packages and individual analyses: Turnaround time: 3 weeks from the day of receipt |
| Clear Lake Environmental Research Center Lab Lakeport, CA | Coliform (Total & E. coli) – Presence/Absence SM 9223 B Colilert $56 source Coliform (Total & E. coli) – Enumeration SM 9223 B Colilert $84 source | – | – | – | – | – | – |
| Crescent City Water Quality Laboratory Crescent City, CA · You collect the sample with the lab's bottles | Presence Absence - $33.00 Presence Absence tests for the presence of Total coliform and E. coli in your water sample. source MPN Quantitray - $45.00 Tests for the presence of Total coliform and E. coli but attaches a numerical number to it. source | – | – | – | – | – | – |
| Humboldt County Public Health Laboratory Eureka, CA · You collect the sample with the lab's bottles | Presence/Absence (COLILERT 24H) Drinking water (Potable) without Enumeration $40.00 source Enumeration, Quanti-tray 51 (COLILERT 24H) Drinking Water (Potable) $45.00 source | – | – | – | – | – | – |
| McCampbell Analytical, Inc. Pittsburg, CA · You collect the sample with the lab's bottles | – | – | – | – | Package Number 1: $240 source | – | Standard turnaround time is 5 business days from the date samples are received at the lab. |
| Napa-Solano-Yolo-Marin Public Health Laboratory Fairfield, CA · You collect the sample with the lab's bottles | Drinking water: Presence/absence for total coliforms & E. coli $38.00 source Drinking water: Quanti-Tray for total coliforms & E. coli $49.00 source | Nitrate or Nitrite individual test $31.00 source | – | – | – | – | – |
| Santa Clara Valley Water District San Jose, CA · Lab staff collect the sample | – | – | – | – | Free testing for domestic well owners source | – | We will send you the laboratory results within about three weeks |
| Sonoma County Public Health Laboratory Santa Rosa, CA · You collect the sample with the lab's bottles | Colilert Presence I Absence (P/A) Coli PA N/A $39.00 source Colilert Quantitray, undiluted (E. coli MPN by Quantitray) Coli-QT-UD N/A $51.50 source | – | – | – | – | – | Results will be ready in approximately 24 hours. |
| Western Environmental Testing Laboratory Sparks, NV · You collect the sample with the lab's bottles | – | – | – | – | – | – | Our standard turn-around time is 10-business days. |
Say they take homeowner samples: Abalone Coast Analytical, Inc., Analytical Environmental Lab, LLC, Antelope Valley-East Kern Water Agency, Brelje and Race Laboratories, Inc., Caltest Analytical Laboratory, Clinical Laboratory of San Bernardino II, Clinical Laboratory of San Bernardino, Inc., Coachella Valley Water District, Crescent City Water Quality Laboratory, Dellavalle Laboratory, Inc., Fruit Growers Laboratory, Inc., Fruit Growers Laboratory, Inc., Fruit Growers Laboratory, Inc., Fruit Growers Laboratory, Inc., Fruit Growers Laboratory, Inc., Imperial County Public Health Laboratory, McCampbell Analytical, Inc., Napa-Solano-Yolo-Marin Public Health Laboratory, SGS North America, Santa Clara Valley Water District, Sonoma County Public Health Laboratory, Western Environmental Testing Laboratory.
Prices exactly as each lab prints them, read 14 Nov 2026 to 15 Nov 2026; re-checked every 90 days. Labs not shown have not been read yet or print nothing for homeowners. Confirm price and turnaround with the lab.
Labs by contaminant
Labs on the California list for one test, with homeowner-accepting labs first.
Well water by county
Private-well population (USGS, 2015), arsenic estimate, radon zone and nearby labs for each county with at least 1,000 people on private wells, largest first.
Fresno County102,121 on wellsContra Costa County88,873 on wellsSonoma County77,261 on wellsSan Joaquin County76,113 on wellsTulare County64,707 on wellsSacramento County56,106 on wellsPlacer County55,329 on wellsMerced County55,324 on wellsSan Diego County51,400 on wellsStanislaus County48,084 on wellsMonterey County46,347 on wellsSanta Clara County44,595 on wellsSan Luis Obispo County42,532 on wellsButte County38,152 on wellsMadera County37,413 on wellsTehama County31,338 on wellsLos Angeles County30,311 on wellsNevada County29,355 on wellsEl Dorado County28,188 on wellsLake County27,596 on wellsSanta Cruz County26,214 on wellsMendocino County24,977 on wellsSolano County23,259 on wellsKern County22,694 on wellsSan Mateo County22,077 on wellsYolo County21,018 on wellsOrange County20,275 on wellsVentura County18,303 on wellsRiverside County17,754 on wellsNapa County17,102 on wellsSiskiyou County14,775 on wellsShasta County13,289 on wellsSutter County12,999 on wellsImperial County12,595 on wellsMariposa County12,533 on wellsCalaveras County11,683 on wellsLassen County11,355 on wellsHumboldt County9,620 on wellsSan Benito County9,531 on wellsGlenn County9,441 on wellsAmador County9,081 on wellsAlameda County8,315 on wellsSanta Barbara County7,976 on wellsKings County7,802 on wellsYuba County7,374 on wellsTrinity County5,753 on wellsModoc County4,533 on wellsSan Francisco County4,158 on wellsColusa County3,433 on wellsMarin County2,913 on wellsTuolumne County2,636 on wellsPlumas County2,631 on wellsDel Norte County2,480 on wellsMono County1,940 on wells