Sonoma County Water Quality: 72 Violations (CA)
48 water systems · 32 ZIP codes · Home Safety Score 95/100 (A) · 21 of 52 tracked ZIP records scored · Updated
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO Last verified:
Violation Trend
EPA violations across water systems in Sonoma County.
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Find the Right Filter →Water Quality Overview
Sonoma County has 48 community water systems across 32 directly mapped ZIP records. The systems report serving approximately 1,932,911 people. The available records contain 72 EPA violations, including 13 health-based violations.
Health-based violations account for 18% of all violations in Sonoma County. These violations indicate contaminant levels that may pose direct risks to human health.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 13 | 18.1% |
| Monitoring/Reporting | 59 | 81.9% |
| Total | 72 | 100% |
Health-based violations indicate contaminant levels exceeding EPA Maximum Contaminant Levels (MCLs). Monitoring violations indicate failures to test or report.
Cities with Most Violations
| Rank | City | Violations | Health-Based | ZIP Codes | Population |
|---|---|---|---|---|---|
| 1 | Santa Rosa | 20 | 6 | 6 | 210,635 |
| 2 | Sonoma | 9 | 3 | 1 | 35,139 |
| 3 | Healdsburg | 5 | 0 | 1 | 15,868 |
| 4 | Cazadero | 5 | 1 | 1 | 1,453 |
| 5 | Jenner | 5 | 1 | 1 | 215 |
| 6 | Petaluma | 4 | 0 | 2 | 71,339 |
| 7 | Rohnert Park | 4 | 0 | 1 | 46,463 |
| 8 | Sebastopol | 4 | 1 | 1 | 28,588 |
| 9 | The Sea Ranch | 4 | 1 | 1 | 1,200 |
| 10 | Cotati | 2 | 0 | 1 | 9,320 |
Violation Trend
Year-by-year EPA violations across water systems in Sonoma County:
| Year | Total | Health-Based |
|---|---|---|
| 2021 | 3 | 3 |
| 2022 | 4 | 4 |
| 2023 | 11 | 11 |
| 2024 | 15 | 15 |
| 2025 | 4 | 4 |
Most Common Contaminants
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Stage 2 DBP Rule | Treatment Technique | 27 | 11 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 11 | 6 | No |
| Barium | Inorganic | 10 | 9 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 4 | 4 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 4 | 4 | No |
Water Data and the Home Safety Score
This page reports EPA water-system facts without converting the broader Home Safety Score into a drinking-water grade. The county Home Safety grade (A) is a separate multi-source index that also requires PFAS screening, radon, and annual air-quality evidence. Check each ZIP report for the versioned score and its component coverage.
Water Systems in Sonoma County
Sonoma County is served by 48 community water systems, averaging 0.9 systems per ZIP code. Each system is independently regulated and tested by the EPA. Larger systems serving more people typically have more extensive monitoring requirements.
Water systems in Sonoma County source water from a mix of surface water (rivers, reservoirs) and groundwater (wells, aquifers). Source type affects which contaminants are most likely to be detected.
How to Check Your Water in Sonoma County
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the Home Safety Score is shown separately with its model version
Request your CCR — every water utility must provide an annual Consumer Confidence Report
Get a home test — certified kits ($20-$50) or professional lab tests ($150-$400) can detect contaminants not covered by routine testing
Consider filtration — NSF-certified filters can address specific contaminants found in your area
Check for lead — homes built before 1986 should test for lead regardless of utility compliance
EPA Enforcement
The EPA and state regulators have taken 114 enforcement actions against water systems in Sonoma County. Enforcement actions range from compliance assistance and administrative orders to formal penalties. Systems under enforcement are required to remediate violations and may face ongoing monitoring requirements.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Source publication schedules vary. See the page source and verification fields for available timing evidence.
Water Quality by ZIP Code in Sonoma County
Water quality varies across Sonoma County's 32 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | City | Violations | Health | |
|---|---|---|---|---|
| 95404 | Santa Rosa | 11 | 3 | View → |
| 95476 | Sonoma | 9 | 3 | View → |
| 95448 | Healdsburg | 5 | 0 | View → |
| 95421 | Cazadero | 5 | 1 | View → |
| 95450 | Jenner | 5 | 1 | View → |
| 95472 | Sebastopol | 4 | 1 | View → |
| 95497 | The Sea Ranch | 4 | 1 | View → |
| 94928 | Rohnert Park | 4 | 0 | View → |
| 95405 | Santa Rosa | 3 | 2 | View → |
| 95409 | Santa Rosa | 3 | 1 | View → |
| 95436 | Forestville | 2 | 0 | View → |
| 95446 | Guerneville | 2 | 0 | View → |
| 94931 | Cotati | 2 | 0 | View → |
| 94952 | Petaluma | 2 | 0 | View → |
| 94954 | Petaluma | 2 | 0 | View → |
| 95407 | Santa Rosa | 2 | 0 | View → |
| 94951 | Penngrove | 2 | 0 | View → |
| 95403 | Santa Rosa | 1 | 0 | View → |
| 95492 | Windsor | 1 | 0 | View → |
| 95425 | Cloverdale | 1 | 0 | View → |
What are EPA health violations?
Health-based violations mean a contaminant was detected above the EPA's Maximum Contaminant Level (MCL) - the legal limit designed to protect human health. Sonoma County has 13 such violations. Not all violations cause illness, but repeated exceedances increase risk, especially for children and immunocompromised individuals.
Water facts and the Home Safety Score
The score shown here is the broader Home Safety Score, not a water-quality grade. Model 4.0.0 combines EPA SDWIS identity plus accepted ECHO SDWA lifecycle-based water compliance, PFAS screening, radon zones, and annual air-quality evidence. Sonoma County has a score of 95/100 (Grade A) across 21 scored of 52 tracked ZIP records.
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Find the Right Filter →Frequently Asked Questions
Is the tap water safe in Sonoma County, California?
Sonoma County has 48 community water systems with 72 recorded EPA violations, including 13 health-based. Water quality varies by ZIP code - check your specific location for detailed results.
How many water violations does Sonoma County have?
Sonoma County has 72 total EPA violations across 32 directly mapped ZIP records. 13 are health-based.
Which city in Sonoma County has the most water violations?
Santa Rosa has the most violations in Sonoma County with 20 recorded EPA violations across 6 ZIP codes.
What contaminants are found in Sonoma County water?
Sonoma County water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. Check your ZIP code for contaminant-specific data.
How can I test my water in Sonoma County?
Contact your local water utility for free or low-cost testing. You can also use a certified home test kit ($20-$50) or hire a certified lab ($150-$400).