Is Brentwood, CA tap water safe?
The short answer
2 of the 4 utilities serving Brentwood have a result above a legal limit or action level, or a health-based violation since 2016, in EPA’s and California’s records: Colonia Santa Maria and Orwood Resort.
Brentwood, which serves the most people here, has 2 results above the health goal and 1 result above EPA’s health benchmark. The worst: Lithium at 102 ppb, above EPA’s health benchmark. Health goals are stricter than legal limits and are not enforced.
The water from Brentwood is very hard, typically 369 mg/L (21.6 grains per gallon). How California’s water compares.
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 Brentwood’s ZIP codes, from EPA’s estimates.
- Open report
Brentwood
California · serves 64,513 people · about 11,100 in Brentwood
2 results above the health goal and 1 result above EPA’s health benchmark. The worst: Lithium at 102 ppb, above EPA’s health benchmark. Hardness: very hard, typically 369 mg/L (21.6 grains per gallon).
No health-based violations since 2016
- Open report
Contra Costa Water District
California · serves 210,500 people · about 1,200 in Brentwood
2 results above the health goal. The worst: Arsenic at 2.5 ppb, above the health goal. Hardness: soft to hard depending on the source, 52 to 132 mg/L (3 to 7.7 grains per gallon).
No health-based violations since 2016
- Open report
Colonia Santa Maria
California · serves 32 people · under 100 in Brentwood
Nothing in its records is above a health goal. Hardness: very hard, 329 mg/L (19.2 grains per gallon).
1 health-based violation since 2016
- Open report
Orwood Resort
California · serves 350 people · under 100 in Brentwood
Nothing in its records is above a health goal. Hardness: very hard, 222 mg/L (13 grains per gallon).
1 health-based violation since 2016
What handles it
Each of these is certified, on a certifier’s listing, for a result above a line in Brentwood’s water, which serves the most people here. Another utility’s report names what handles its own results.
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Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Arsenic
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Water testing near Brentwood
The 3 labs California certifies closest to Brentwood, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
McCampbell Analytical, Inc.
Pittsburg, CA · about 16 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS
Alpha Analytical Laboratories, Inc.
Livermore, CA · about 20 miles
Certified for bacteria
Precision Enviro-Tech
Stockton, CA · about 21 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics
ZIP codes in Brentwood
Which ZIP codes are in Brentwood: 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 Brentwood
Other towns in Contra Costa County with a page of their own.
What to do next
- Read Brentwood’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