California Water Quality Report: 2,690 Violations Across 1,479 ZIPs
2,704 water systems · 1,479 ZIP codes · 2,690 violations · Updated
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO Last verified:
ZipCheckup tracks EPA drinking-water compliance for 2,704 public water systems serving 1,479 ZIP codes in California. The state record shows 2,690 EPA violations, 1,138 health-based.
City Water Quality Map: California
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Violation Trend
EPA violations across all water systems in California.
Cities with Most Violations in California
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Santa Maria | 59 | 7 | 145,186 | Details → | |
| 2 | Bakersfield | 52 | 18 | 589,959 | Details → | |
| 3 | Corona | 51 | 11 | 262,651 | Details → | |
| 4 | Riverside | 47 | 10 | 443,626 | Details → | |
| 5 | Norco | 45 | 4 | 25,268 | Details → | |
| 6 | Morongo Valley | 43 | 5 | 3,907 | Details → | |
| 7 | Valley Center | 42 | 5 | 20,596 | Details → | |
| 8 | Pauma Valley | 42 | 5 | 1,693 | Details → | |
| 9 | Pala | 42 | 5 | 1,449 | Details → | |
| 10 | Porterville | 41 | 5 | 80,581 | Details → |
Most Common Contaminants in California
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Stage 2 DBP Rule | Treatment Technique | 574 | 225 | Yes |
| Lead | Inorganic | 465 | 141 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 291 | 131 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 243 | 128 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 182 | 153 | No |
| Barium | Inorganic | 153 | 33 | Yes |
| Combined Radium | Radionuclides | 125 | 8 | Yes |
| Contaminant 1045 | Other | 63 | 12 | Yes |
| E. coli | Microbiological | 61 | 53 | Yes |
| Total Coliform | Microbiological | 43 | 38 | No |
Water Quality Overview
California has 2,704 community water systems represented across 1,479 directly mapped ZIP records. The associated city records cover approximately 39,426,086 people. The available records contain 2,690 EPA violations, including 1,138 health-based violations.
Health-based violations account for 42% of all violations in California. These violations indicate contaminant levels that may pose direct risks to human health, as opposed to monitoring or reporting failures.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 1,138 | 42.3% |
| Monitoring/Reporting | 1,552 | 57.7% |
| Total | 2,690 | 100% |
Health-based violations indicate contaminant levels exceeding EPA Maximum Contaminant Levels (MCLs). Monitoring violations indicate failures to test or report - these do not necessarily mean unsafe water, but they mean the water was not properly verified.
Cities with Most Violations
The following cities in California have the highest number of EPA violations:
| Rank | City | Violations | Water Systems | Population |
|---|---|---|---|---|
| 1 | Santa Maria | 59 | 7 | 145,186 |
| 2 | Bakersfield | 52 | 18 | 589,959 |
| 3 | Corona | 51 | 11 | 262,651 |
| 4 | Riverside | 47 | 10 | 443,626 |
| 5 | Norco | 45 | 4 | 25,268 |
| 6 | Morongo Valley | 43 | 5 | 3,907 |
| 7 | Valley Center | 42 | 5 | 20,596 |
| 8 | Pauma Valley | 42 | 5 | 1,693 |
| 9 | Pala | 42 | 5 | 1,449 |
| 10 | Porterville | 41 | 5 | 80,581 |
Violation counts are cumulative across all water systems serving each city. Higher counts may reflect larger systems with more monitoring requirements, not necessarily worse water quality.
Violation Trend Over Time
Year-by-year EPA violations recorded across all water systems in California:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2021 | 206 | 206 |
| 2022 | 572 | 569 |
| 2023 | 622 | 622 |
| 2024 | 1,208 | 1,208 |
| 2025 | 345 | 345 |
Violations have increased from 206 in 2021 to 345 in 2025. This trend warrants monitoring and may reflect expanded testing requirements rather than worsening quality.
Most Common Contaminants
The following contaminants have caused the most violations across California water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Stage 2 DBP Rule | Treatment Technique | 574 | 225 | Yes |
| Lead | Inorganic | 465 | 141 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 291 | 131 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 243 | 128 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 182 | 153 | No |
| Barium | Inorganic | 153 | 33 | Yes |
| Combined Radium | Radionuclides | 125 | 8 | Yes |
| E. coli | Microbiological | 61 | 53 | Yes |
| Total Coliform | Microbiological | 43 | 38 | No |
| Surface Water Treatment Rule | Treatment Technique | 41 | 35 | No |
How to Check Your Water in California
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the separate Home Safety Score is a multi-source index
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)
Consider filtration - NSF-certified filters can address specific contaminants found in your area
EPA Enforcement
The EPA and state regulators have taken 4,607 enforcement actions against water systems in California. Enforcement actions range from compliance assistance to formal orders and penalties.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Updated daily.
What are EPA 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. California has 1,138 such violations across its water systems. Not all violations cause illness, but repeated exceedances increase risk, especially for children and immunocompromised individuals.
Understanding water quality grades
ZipCheckup grades water systems from A to F based on EPA violation history, contaminant levels, and system compliance. Grade A means few or no violations; Grade F indicates persistent or serious issues. Grades are calculated per ZIP code and aggregated at the city, county, and state level.
Wondering about your tap water?
Water quality varies by ZIP code. Enter yours to see contaminant data, violations, and filtration recommendations specific to your area.
Check Your ZIP Code Water Quality →Frequently Asked Questions
Is the tap water safe to drink in California?
California has 2,704 community water systems with 2,690 recorded EPA violations, including 1,138 health-based. Water quality varies by city and ZIP code - check your specific location for detailed results.
How many water violations does California have?
California has 2,690 total EPA violations across 1,479 ZIP codes. 1,138 are health-based violations that indicate contaminant levels potentially harmful to human health. The remainder are monitoring or reporting violations.
Which city in California has the worst water quality?
Santa Maria, CA has the most EPA violations among major cities in California with 59 recorded violations. Check individual ZIP codes for the most accurate picture of your local water quality.
Which city in California has the best water quality?
Several cities in California maintain excellent EPA compliance. Check individual city reports for details.
What contaminants are found in California drinking water?
California water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. The most common violations vary by region - check your ZIP code for contaminant-specific data.