Contra Costa County, California
35 ZIP codes · Avg score 68/100 · Grade C · Updated 2026-06-04
Contra Costa County: 35 ZIP codes, mid-range safety grade.
How Contra Costa County Compares
How Contra Costa County Compares
Contra Costa County scores 5 points below the California state average (73/100) and 0 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-04
ZIP Code Risk Map
Water Quality Map: Contra Costa County, California
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 10.7 (asthma 9.4%, diabetes 11.3%)
Estimated additional annual cost per homeowner: $2,073, driven primarily by flood
Infrastructure: 0.335% avg pipe failure probability, 17% of ZIPs at high risk
60.8% of homes built before 1978 (lead paint era)
Violation History (2021–2025)
↑ Worsening trendEPA violation counts by year across Contra Costa County water systems. Health-based shown in red, total in blue.
Peak year: 2024 with 34 violations. Past 5 years: 92 total (92 health-based). Health-based violations are rising versus the prior 2-year window — worth closer monitoring.
Source: EPA SDWIS historical violations. Data may lag 6–12 months for the most recent year.
County Health Indicators vs National Average
Black markers indicate national averages. Source: CDC PLACES, Census ACS.
Infrastructure Overview
Sources: Census ACS (housing age), EPA SDWIS (infrastructure risk model), state bridge inspection data.
Compound Risk Breakdown
Estimated additional annual cost per homeowner: $2,073
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
330,354 housing units in Contra Costa County
Source: U.S. Census Bureau ACS B25034 (Year Structure Built).
Water Safety Affordability
How much it costs to fix water issues relative to home values in Contra Costa County
Remediation costs are relatively manageable for most homeowners in Contra Costa County, representing a small fraction of property value.
Remediation includes water filtration, lead abatement, radon mitigation, and flood protection where applicable. Source: Census ACS, EPA SDWIS.
Health Outcomes vs National Average
CDC PLACES data for Contra Costa County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 5 systems in Contra Costa County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Contra Costa Water District | 198,000 | 73 |
| 2 | EAST BAY MUD | 1,442,800 | 66 |
| 3 | DIABLO WATER DISTRICT | 43,357 | 37 |
| 4 | City of Antioch | 115,074 | 36 |
| 5 | Bella Vista Water Sys | 93 | 36 |
46 total water systems serve Contra Costa County.
All ZIP Codes in Contra Costa County
35 ZIP codes tracked in Contra Costa County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 94516 | Canyon | 81 | B | 1 | $787K |
| 2 | 94517 | Clayton | 81 | B | 1 | $996K |
| 3 | 94519 | Concord | 79 | B | 4 (1 health) | $728K |
| 4 | 94524 | Concord | 79 | B | 4 (1 health) | — |
| 5 | 94505 | Discovery Bay | 78 | B | 0 | $788K |
| 6 | 94527 | Concord | 78 | B | 4 (1 health) | — |
| 7 | 94529 | Concord | 78 | B | 4 (1 health) | — |
| 8 | 94565 | Pittsburg | 78 | B | 0 | $563K |
| 9 | 94506 | Danville | 76 | B | 0 | $1790K |
| 10 | 94597 | Walnut Creek | 76 | B | 1 | $987K |
| 11 | 94598 | Walnut Creek | 76 | B | 1 | $1307K |
| 12 | 94531 | Antioch | 75 | B | 0 | $660K |
| 13 | 94511 | Bethel Island | 74 | B | 2 | $550K |
| 14 | 94518 | Concord | 74 | B | 4 (1 health) | $827K |
| 15 | 94520 | Concord | 74 | B | 4 (1 health) | $572K |
| 16 | 94521 | Concord | 74 | B | 4 (1 health) | $823K |
| 17 | 94523 | Pleasant Hill | 73 | B | 0 | $1038K |
| 18 | 94547 | Hercules | 73 | B | 4 (2 health) | $741K |
| 19 | 94553 | Martinez | 73 | B | 0 | $781K |
| 20 | 94526 | Danville | 71 | B | 0 | $1588K |
| 21 | 94595 | Walnut Creek | 71 | B | 1 | $817K |
| 22 | 94596 | Walnut Creek | 71 | B | 1 | $1245K |
| 23 | 94513 | Brentwood | 70 | B | 6 (2 health) | $794K |
| 24 | 94563 | Orinda | 70 | B | 0 | $1810K |
| 25 | 94509 | Antioch | 65 | C | 0 | $565K |
| 26 | 94548 | Knightsen | 63 | C | 0 | $918K |
| 27 | 94507 | Alamo | 55 | C | 0 | $2000K |
| 28 | 94514 | Byron | 55 | C | 0 | $853K |
| 29 | 95683 | Sloughhouse | 55 | C | 0 | $666K |
| 30 | 94561 | Oakley | 53 | D | 29 (29 health) | $632K |
| 31 | 94583 | San Ramon | 53 | D | 16 (10 health) | $1234K |
| 32 | 94549 | Lafayette | 50 | D | 0 | $1969K |
| 33 | 94582 | San Ramon | 50 | D | 16 (10 health) | $1544K |
| 34 | 94570 | Moraga | 45 | D | 18 (14 health) | — |
| 35 | 94575 | Moraga | 45 | D | 18 (14 health) | — |
Recommended Buyer Guides for Contra Costa County
Below: editorial picks, no sponsored placements.
- Best Lead Paint Test Kits — 60.8% of homes built before 1978
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
- Best Sump Pumps — Flood is the top compound risk factor
- Best Mold Test Kits — Flood-driven moisture and mold risk
Deep Dive Reports
Detailed analysis for Contra Costa County, California
Overview
Contra Costa County in California covers 35 ZIP codes with an average Home Safety Score of C (68/100).
21 of 35 ZIP codes have recorded EPA violations. 88 health-based violations have been documented.
← Back to California water quality report
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Home values: U.S. Census Bureau ACS (median estimates by ZCTA)
Updated daily.