Los Angeles County Water Quality: 314 Violations (CA)
146 water systems · 286 ZIP codes · Home Safety Score 69/100 (C) · 269 of 516 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 Los Angeles County.
Concerned about water quality in Los Angeles County?
Get connected with a certified testing service.
Find the Right Filter →Water Quality Overview
Los Angeles County has 146 community water systems across 286 directly mapped ZIP records. The systems report serving approximately 10,413,591 people. The available records contain 314 EPA violations, including 65 health-based violations.
Health-based violations account for 21% of all violations in Los Angeles County. These violations indicate contaminant levels that may pose direct risks to human health.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 65 | 20.7% |
| Monitoring/Reporting | 249 | 79.3% |
| Total | 314 | 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 | Lancaster | 58 | 39 | 3 | 194,781 |
| 2 | Whittier | 27 | 0 | 6 | 187,139 |
| 3 | Pico Rivera | 26 | 0 | 1 | 60,821 |
| 4 | Burbank | 25 | 0 | 5 | 108,959 |
| 5 | Pomona | 24 | 2 | 3 | 153,902 |
| 6 | Palmdale | 13 | 1 | 4 | 186,319 |
| 7 | El Monte | 12 | 3 | 2 | 86,178 |
| 8 | Montebello | 12 | 1 | 1 | 61,615 |
| 9 | Rosemead | 9 | 0 | 1 | 58,893 |
| 10 | Pearblossom | 9 | 2 | 1 | 1,349 |
Violation Trend
Year-by-year EPA violations across water systems in Los Angeles County:
| Year | Total | Health-Based |
|---|---|---|
| 2021 | 16 | 16 |
| 2022 | 109 | 106 |
| 2023 | 117 | 117 |
| 2024 | 217 | 217 |
| 2025 | 71 | 71 |
Most Common Contaminants
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Barium | Inorganic | 36 | 2 | Yes |
| Stage 2 DBP Rule | Treatment Technique | 31 | 13 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 23 | 20 | No |
| Stage 1 DBP Rule | Treatment Technique | 23 | 16 | No |
| Lead | Inorganic | 18 | 11 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 18 | 15 | Yes |
| Chlorodibromoacetic Acid | Disinfection Byproducts | 12 | 9 | No |
| HAA6Br | Disinfection Byproducts | 12 | 9 | No |
| Bromochloroacetic Acid | Disinfection Byproducts | 10 | 10 | No |
| E. coli | Microbiological | 10 | 2 | Yes |
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 (C) 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 Los Angeles County
Los Angeles County is served by 146 community water systems, averaging 0.3 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 Los Angeles 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 Los Angeles 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 739 enforcement actions against water systems in Los Angeles 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 Los Angeles County
Water quality varies across Los Angeles County's 286 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | City | Violations | Health | |
|---|---|---|---|---|
| 93534 | Lancaster | 29 | 19 | View → |
| 90660 | Pico Rivera | 26 | 0 | View → |
| 93536 | Lancaster | 25 | 19 | View → |
| 91768 | Pomona | 24 | 2 | View → |
| 90606 | Whittier | 24 | 0 | View → |
| 90640 | Montebello | 12 | 1 | View → |
| 91732 | El Monte | 12 | 3 | View → |
| 91770 | Rosemead | 9 | 0 | View → |
| 93553 | Pearblossom | 9 | 2 | View → |
| 93551 | Palmdale | 8 | 1 | View → |
| 90755 | Signal Hill | 7 | 5 | View → |
| 90806 | Long Beach | 7 | 5 | View → |
| 93543 | Littlerock | 7 | 1 | View → |
| 91006 | Arcadia | 7 | 1 | View → |
| 93544 | Llano | 7 | 1 | View → |
| 91501 | Burbank | 5 | 0 | View → |
| 91502 | Burbank | 5 | 0 | View → |
| 91504 | Burbank | 5 | 0 | View → |
| 91505 | Burbank | 5 | 0 | View → |
| 91506 | Burbank | 5 | 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. Los Angeles County has 65 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. Los Angeles County has a score of 69/100 (Grade C) across 269 scored of 516 tracked ZIP records.
Not sure if your water needs a filter?
Our free tool matches your ZIP code data to the right filtration system - based on actual contaminants detected in your area.
Find the Right Filter →Frequently Asked Questions
Is the tap water safe in Los Angeles County, California?
Los Angeles County has 146 community water systems with 314 recorded EPA violations, including 65 health-based. Water quality varies by ZIP code - check your specific location for detailed results.
How many water violations does Los Angeles County have?
Los Angeles County has 314 total EPA violations across 286 directly mapped ZIP records. 65 are health-based.
Which city in Los Angeles County has the most water violations?
Lancaster has the most violations in Los Angeles County with 58 recorded EPA violations across 3 ZIP codes.
What contaminants are found in Los Angeles County water?
Los Angeles 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 Los Angeles 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).