Metropolitan Water District of Southern California - Robert B. Diemer Water Treatment Plant Laboratory

Looks like a utility or municipal lab

Judging by the name only (this is our label, not the state's). Labs like this usually test their own system. The state list does not say whether it takes samples from the public, so ask before you send one.

At a glance

What it is certified to test

1 of the 9 common well tests on the CA list (see which)

Price

not published on the state list: ask the lab for a quote

Turnaround

not stated on the state list or the lab’s website: ask when you order

Homeowner samples

not stated: ask the lab

Lab facts

Listed by

California (California State Water Resources Control Board - Environmental Laboratory Accreditation Program (ELAP))

Address

3972 Valley View Avenue, Yorba Linda, CA 92886 · Open in Google Maps

Phone

(909) 392-5240

Public / homeowner samples

Public samples: ask the lab

CA ELAP lab type 'Public Water System': the state list does not say whether it takes samples from the public

Left blank on the list

The California list (version Map layer fetched 2026-11-15; scope PDF as of 11/1/2023) gives no website for this lab.

Certification record

Certificate ID

CA ELAP 1618-S2

Issued by

California State Water Resources Control Board - Environmental Laboratory Accreditation Program (ELAP) (certification program)

Expiry on the list

10/31/2025 · Date on list has passed (380 days ago)

List version

California ELAP - Accredited Laboratories (map layer) + per-lab Fields of Accreditation, version Map layer fetched 2026-11-15; scope PDF as of 11/1/2023

We fetched it

15 Nov 2026 (file SHA-256 cbc97398a144…) · open the state file

Tests on the state list

• Named on the official list The state list names this analyte (or a column for it) for this lab.
• Group-level certification Certified for a parent group (e.g. 'Inorganics') that includes this analyte. Confirm the specific test with the lab.
• Partial group certification The list marks the group as 'Partial'. Confirm this analyte with the lab.
• Subcontracted The lab sends this analyte to another accredited lab (MDH 'X*').

4 drinking-water analytes across 3 methods in ELAP Fields of Accreditation 101 Microbiology of Drinking Water, 102 Inorganic Chemistry of Drinking Water. Scope PDF: https://www.waterboards.ca.gov/drinking_water/certlic/labs/documents/elap_certs/11482.pdf (as of 11/1/2023). The scope PDF's expiration date (10/31/2025) has passed; the ELAP map layer still lists the lab as Certified, so check its current standing with ELAP.

Nearest labs that take homeowner samples

16 other certified labs that take homeowner samples are within 25 miles of this lab. Distances are straight-line from the address on the state list (approx. = ZIP-code centre). “Takes homeowner samples” comes from a state list column or the lab’s own website, as named.

Price and turnaround as printed on each lab’s own website and checked by a second reader; – = not published or not read yet.

Around this lab: Orange County, CA

• Private wells: about 20,275 people, 1% of Orange County’s 3,169,776 residents (USGS, 2015); rank 27 of 58 counties in California by people on wells.

• EPA radon zone (indoor air): Zone 3: low potential (average indoor radon may be less than 2 pCi/L). EPA says the zone map should not decide whether one home needs testing.
• Arsenic above 10 µg/L (USGS model): about 1,975 private-well users (95% range 1,591 to 2,430; 2010 base), rank 21 of 58 in the state. A screening estimate, not a measurement of any well.
• Older homes (Census ACS 2020–2024): 57% of 1,146,169 housing units were built before 1980, about the same as the state share of 56%. Homes built before 1986 are more likely to have lead solder or fittings, so test tap water for lead there.
• PFAS in public water nearby (public supply, not your well): 37 public systems serving this county reported EPA UCMR 5 results; 15 had a PFOA or PFOS sample at or above 4.0 ng/L.

County figures describe where the lab is, not the lab. Sources: USGS 2015 water use and 2017 arsenic estimates, EPA radon zones, Census ACS table B25034 (2020–2024), EPA UCMR 5 (2023–2026); details and links on the sources page.

Before you send a sample

Call the lab to confirm it's currently certified for the exact test and method, that it accepts samples from homeowners, and how to collect and ship them. Bacteria samples have short holding times. Status can change between list updates. To check a status, contact the California certification program.

Is this your lab?

Labs can ask for corrections through the agency that publishes their state list. Homeowner service, prices and turnaround above come only from the lab’s own website. To ask us to correct or remove this listing, write to us (how we handle listings).