Is Diamond Bar, CA tap water safe?
The short answer
None of the 4 utilities serving Diamond Bar has a result above a legal limit or action level, or a health-based violation since 2016, in EPA’s and California’s records.
Walnut Valley Water District, which serves the most people here, has 1 result above EPA’s health benchmark. The worst: Lithium at 50.1 ppb, above EPA’s health benchmark. A health benchmark is a level EPA screens with, not a legal limit.
A town can be served by more than one utility, and some homes are on private wells. The name on your water bill tells you which is yours, and your ZIP code narrows it down. They are listed by how many people each serves in Diamond Bar’s ZIP codes, from EPA’s estimates.
- Open report
Walnut Valley Water District
California · serves 100,941 people · about 18,100 in Diamond Bar
1 result above EPA’s health benchmark. The worst: Lithium at 50.1 ppb, above EPA’s health benchmark.
No health-based violations since 2016
- Open report
Suburban Water Systems - San Jose
California · serves 170,523 people · about 510 in Diamond Bar
3 results above the health goal and 1 result above EPA’s health benchmark. The worst: Lithium at 56 ppb, above EPA’s health benchmark. Hardness: hard to very hard depending on the source, 147 to 290 mg/L (8.6 to 17 grains per gallon).
No health-based violations since 2016
- Open report
Fire Suppression Camp #19
California · serves 125 people · based in Diamond Bar
2 results above the health goal. The worst: Arsenic at 2.5 ppb, above the health goal. Hardness: very hard, 219 mg/L (12.8 grains per gallon).
No health-based violations since 2016
- Open report
California Conservation Camp #14
California · serves 107 people · based in Diamond Bar
3 results above the health goal. The worst: Uranium at 4.5 ppb, above the health goal. Hardness: very hard, typically 487 mg/L (28.5 grains per gallon).
No health-based violations since 2016
Water testing near Diamond Bar
The 3 labs California certifies closest to Diamond Bar, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Eurofins Pomona
Pomona, CA · about 5 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS, radioactivity
Enviro-Chem, Inc.
Pomona, CA · about 7 miles
Certified for metals
Western Analytical Laboratories, Inc.
Chino, CA · about 8 miles
Certified for bacteria, minerals and other inorganics
Which ZIP codes are in Diamond Bar: Census 2020 relationship files. Which utilities serve them, and how many people: EPA SDWIS and EPA’s service area map. Each utility’s results: EPA UCMR 5, EPA SDWIS, and EPA’s and the state’s compliance monitoring, as its report lists them. How they are measured: methodology. Certified labs: California State Water Resources Control Board, ELAP accredited laboratories and their fields of accreditation; distances from the Census 2020 ZIP code tabulation area gazetteer.
Near Diamond Bar
Other towns in Los Angeles County with a page of their own.
What to do next
- Read Walnut Valley Water District’s full reportEvery result with its dates, the violations, and the certification claim that handles each finding.Open the report
- About LithiumWhat it does to health, where it comes from, and the certification claim that addresses it.About Lithium
- On a private well?No utility tests a well. A certified lab test is the first step.How to test well water