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County · California

Contra Costa County, California: drinking water records

Explore EPA records for 39 community water systems across 43 ZIP codes in Contra Costa County, then find water-testing resources and available recent monitoring-station readings.

In focus39Community water systems
Public records. Clearer context.

Data as of EPA UCMR 5 final release, August 2026 (file dated Aug 28, 2026) · EPA SDWIS 2026Q2 (file dated Jul 9, 2026). How we build these pages

Drinking-water records

EPA survey and compliance records are historical reports. UCMR 5 results are available for 8 of the 39 listed systems in this snapshot. A system with no reported PFAS detection is not a test of every tap or every contaminant.

8
systems in EPA's PFAS survey
0
systems where PFAS was found
0
systems at or above the PFOA or PFOS limit, on the yearly-average basis EPA uses
6
systems that have reached the lead action level
10
systems with a health-based violation since 2016

System population figures are summed from EPA registry records and can overlap where wholesalers and retail systems serve the same people. They are not a Census county-population estimate.

Water systems in this county

All 39 active community systems in the available county records, sorted by record completeness. Scroll the table to explore more systems.

Water systemPeople servedPFAS survey resultsPFAS foundHealth-based violationsLead, 9 in 10 homes at or below
Contra Costa Water District CA0710003198,000360003.1 ppb
City of Antioch CA0710001115,074120000 ppb
Brentwood CA071000464,513420000 ppb
City of Pittsburg CA071000862,500120000 ppb
Diablo Water District CA071000743,35795001.9 ppb
City of Martinez CA071000630,997120000 ppb
Golden State Water Company - Bay Point CA071000223,731120000 ppb
Town of Discovery Bay CA071000916,79095000 ppb
Willow Park Marina CA070750738000211.3 ppb
Orwood Resort CA07075453500010 ppb
Delta Mutual Water Company CA070757333300200 ppb
Oakley Mutual Water Company CA070600417000190 ppb
Russos Mobile Park CA07076011100010 ppb
Sandmound Mutual CA07075561000010 ppb
Bella Vista Water Sys CA07075899300146.5 ppb
Sandy Point Mobile Home Park CA0707597670011 ppb
Doubletree Ranch Water System CA0707615660070 ppb
Colonia Santa Maria CA0707517320010 ppb
Pleasantimes Mutual Water Co CA07075766440000.5 ppb
Clayton Palms Water CA07076035490004 ppb
Willow Mobile Home Park CA070761348100010 ppb
Riverview Water Association CA07075772300000 ppb
Camino Mobilehome CA07075982100000 ppb
Bethel Island Estates CA07075232000000 ppb
Bethel Island MHC CA07075751850002.6 ppb
Big Oak Mobile Home Park Water CA07075881560000 ppb
Farrar Park Property Owners CA07060051400000 ppb
Riverview Mobile Home Park CA07075531260000 ppb
Bethel Island Mutual Water Co CA07075721230000 ppb
Anglers Subdivision 4 CA0707569990000 ppb
Marina Mobile Manor CA07076087500024 ppbat or above the action level
Knightsen Community Water System CA0707547730001.1 ppb
Moraga Heights Mutual Water CA0707585660002 ppb
Angler S Ranch #3 CA0707501600000 ppb
Dutch Slough Water Works CA0707519490000 ppb
Casa Medanos Water System CA0707594450000 ppb
Wilcox Station Ranch CA0707623310000 ppb
Randall-Bold Water Treatment Plant CA07100101000not reported
Ccwd/Brentwood WTP CA07100110000not reported

Shaded rows report lead at or above the 15 ppb action level in their latest monitoring period. EPA sets that level for the value 9 in 10 sampled homes fall at or below; reaching it requires the utility to act, and it is not a measurement of any single tap. One system in this table is at or above it. What an action level means

USGS · Monitoring stations

The water, more recently.

Available station readings in Contra Costa County, California. Each measurement keeps its time, unit and original source.

These readings describe water at a monitoring station. They do not test your tap, measure PFAS or lead, or determine whether water is safe to drink or swim in.

Recent observations load when this section comes into view.

Station coverage and available measurements vary by county.

Explore USGS Water Data
How these readings update

We check for updates every 10 minutes while this section is visible and show supported observations from the last 48 hours. The time beside a reading is when USGS measured it; the checked time is when our service retrieved the response. We mark a reading more than 6 hours old as older. Provisional observations can change after USGS review. A missing reading does not mean zero or clean water.

Temperature, pH, dissolved oxygen, turbidity, conductivity, streamflow and water level are shown only where a station reports them. Different measurements have different units and sampling intervals. USGS data and documentation.

Your next step

Water testing, reports & local help.

Use these official directories to find your drinking-water agency, a certified laboratory and public water records. We have not yet added an individually reviewed local resource list for this county.

Official national directories

Water testing

Find your state’s private-well program

EPA’s state directory points well owners to local program information. Services and eligibility vary by state and county.

U.S. Environmental Protection Agency
Source reviewed · Source updated

Water testing

Find a certified drinking-water laboratory

Use EPA’s directory to reach your state’s laboratory certification program. EPA does not provide on-request testing of residential drinking water.

U.S. Environmental Protection Agency
Source reviewed · Source updated

Public records

Find your utility’s Consumer Confidence Report

EPA links to community water-system reports and explains how to read them. Look for your actual supplier rather than assuming every address in a county shares one system.

U.S. Environmental Protection Agency
Source reviewed · Source updated

Public records

Explore USGS water observations

Find current and historical observations from USGS monitoring locations, including available stream, lake, and groundwater data. Measurements vary by station and do not replace a test of your household water.

U.S. Geological Survey
Source reviewed

A county overview cannot identify every property’s water provider. If you use a public water system, confirm its name on your bill and request its annual Consumer Confidence Report. Private wells need their own testing; public-system records do not describe a private well.

Understand water testing and laboratory reports

Resource descriptions are compiled by Tap Water Lookup. Review dates describe our source check, not a new water sample. How we review sources · Suggest a correction

Explore your area

Local coverage in Contra Costa County

43ZIP areas in this overview

Explore the water-system records, recent station readings and testing resources on this county page. They describe the systems and stations identified in each section; they are not a separate water test for every community.

Towns and communities

  • Alamo
  • Antioch
  • Berkeley
  • Bethel Island
  • Blackhawk
  • Brentwood
  • Byron
  • Clayton
  • Concord
  • Crockett
  • Danville
  • Diablo
  • Discovery Bay
  • El Cerrito
  • Hercules
  • Knightsen
  • Lafayette
  • Martinez
  • Moraga
  • Oakley
  • Orinda
  • Pinole
  • Pittsburg
  • Pleasant Hill
  • Port Costa
  • Richmond
  • Rodeo
  • San Ramon
  • Walnut Creek
Explore water-system recordsFind water-testing resources
View ZIP areas and understand coverage
  • 94505Discovery Bay
  • 94506Blackhawk
  • 94507Alamo
  • 94509Antioch
  • 94511Bethel Island
  • 94513Brentwood
  • 94514Byron
  • 94516
  • 94517Clayton
  • 94518Concord
  • 94519Concord
  • 94520Concord
  • 94521Concord
  • 94523Pleasant Hill
  • 94525Crockett
  • 94526Danville
  • 94528Diablo
  • 94530El Cerrito
  • 94531Antioch
  • 94547Hercules
  • 94548Knightsen
  • 94549Lafayette
  • 94553Martinez
  • 94556Moraga
  • 94561Oakley
  • 94563Orinda
  • 94564Pinole
  • 94565Pittsburg
  • 94569Port Costa
  • 94572Rodeo
  • 94575Moraga
  • 94582San Ramon
  • 94583San Ramon
  • 94595Walnut Creek
  • 94596Walnut Creek
  • 94597Walnut Creek
  • 94598Walnut Creek
  • 94708Berkeley
  • 94801Richmond
  • 94803Richmond
  • 94804Richmond
  • 94805Richmond
  • 94806Richmond

These Census ZIP Code Tabulation Areas are grouped here by their largest county overlap. A ZIP area can cross county lines and contain several water suppliers or private wells. Place labels reflect Census geography, not verified postal city names or utility service boundaries.

Records for these areas are currently presented in this county overview rather than individual ZIP reports. An unpublished report does not mean there are no water records. Confirm your supplier on your water bill; if you use a private well, testing your own well is the relevant next step.

Beyond this county page

Keep reading. Compare nearby.

PFASReading PFAS survey resultsWhat a detection, a reporting level and a yearly average mean in EPA’s PFAS survey records.LeadChoosing a lead filter6 systems here have reached the lead action level. See how to check a filter’s lead-reduction certification.Your utilityFind your annual water reportConfirm the supplier on your bill, then read its Consumer Confidence Report for local results.

Counties near Contra Costa County

All California counties

Sources and scope

EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Database prepared 2026-09-03.

Counts cover the systems that report this county to EPA. A water system may cross county lines. "Found" means at least one result at or above the laboratory reporting level; it is not a compliance finding.

Compiled by Tap Water Lookup from the sources identified on this page. Read the methodology and review process.

Keep exploring

Every record tells
part of the story.

Find a place. Read the measurements.
Understand the context.

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