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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality data for 43 cities serving 8,042,543 residents
Los Angeles County in California has an average water quality score of 82/100 (Grade B+) based on analysis of 43 municipal water systems. The county's water systems serve approximately 8,042,543 residents.
Overall, Los Angeles County demonstrates good water quality standards. 27 of 43 cities exceed the county average, with Monterey Park leading with a score of 96/100.
43 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Inglewood Top concern: Fluoride (17.7% of limit) | 96 | A+ | 107,337 |
| 2 | Monterey Park Top concern: Haloacetic Acids (15.4% of limit) | 96 | A+ | 57,504 |
| 3 | Norwalk Top concern: Fluoride (17.8% of limit) | 93 | A | 101,405 |
| 4 | Manhattan Beach Top concern: Total Trihalomethanes (17.9% of limit) | 90 | A | 38,954 |
| 5 | El Monte Top concern: Haloacetic Acids (20% of limit) | 89 | A- | 115,179 |
| 6 | Huntington Park Top concern: Fluoride (19.9% of limit) | 89 | A- | 60,311 |
| 7 | Diamond Bar Top concern: Total Trihalomethanes (20.8% of limit) | 89 | A- | 53,363 |
| 8 | Santa Clarita Top concern: Fluoride (15.4% of limit) | 88 | A- | 229,834 |
| 9 | South Gate Top concern: Total Trihalomethanes (18.2% of limit) | 88 | A- | 91,287 |
| 10 | Santa Monica Top concern: Nitrite (14.4% of limit) | 87 | A- | 89,861 |
| 11 | West Covina Top concern: Haloacetic Acids (22.2% of limit) | 86 | A- | 108,261 |
| 12 | Glendale Top concern: Total Trihalomethanes (36.2% of limit) | 85 | A- | 199,388 |
| 13 | Palmdale Top concern: Haloacetic Acids (22% of limit) | 85 | A- | 154,605 |
| 14 | Torrance Top concern: Haloacetic Acids (22.5% of limit) | 85 | A- | 147,045 |
| 15 | Downey Top concern: Nitrate (14.4% of limit) | 85 | A- | 109,979 |
| 16 | Carson Top concern: Haloacetic Acids (20.6% of limit) | 85 | A- | 94,506 |
| 17 | Lakewood Top concern: Total Trihalomethanes (19.8% of limit) | 85 | A- | 79,366 |
| 18 | Lynwood Top concern: Total Trihalomethanes (40% of limit) | 85 | A- | 69,586 |
| 19 | Rosemead Top concern: Mercury (29.4% of limit) | 85 | A- | 57,747 |
| 20 | Long Beach Top concern: Lead (18.9% of limit) | 84 | B+ | 463,380 |
| 21 | Hawthorne Top concern: Fluoride (18.5% of limit) | 84 | B+ | 91,336 |
| 22 | Whittier Top concern: Total Trihalomethanes (21.6% of limit) | 84 | B+ | 83,058 |
| 23 | Alhambra Top concern: Copper (35.1% of limit) | 84 | B+ | 82,888 |
| 24 | Glendora Top concern: Lead (39% of limit) | 84 | B+ | 50,965 |
| 25 | La Mirada Top concern: Lead (36% of limit) | 84 | B+ | 48,378 |
| 26 | Redondo Beach Top concern: Fluoride (19.7% of limit) | 83 | B+ | 72,560 |
| 27 | Covina Top concern: Total Trihalomethanes (44.4% of limit) | 83 | B+ | 48,616 |
| 28 | Pasadena Top concern: Lead (36.5% of limit) | 81 | B+ | 137,476 |
| 29 | Baldwin Park Top concern: Total Trihalomethanes (44.9% of limit) | 81 | B+ | 74,178 |
| 30 | Burbank Top concern: Total Trihalomethanes (38.6% of limit) | 80 | B+ | 102,453 |
| 31 | Pico Rivera Top concern: Copper (36% of limit) | 80 | B+ | 62,759 |
| 32 | Paramount Top concern: Arsenic (27.7% of limit) | 78 | B | 51,714 |
| 33 | Pomona Top concern: Total Trihalomethanes (41.2% of limit) | 74 | B- | 148,282 |
| 34 | Los Angeles Top concern: Total Trihalomethanes (32.6% of limit) | 73 | B- | 3,899,009 |
| 35 | Azusa Top concern: Haloacetic Acids (20.6% of limit) | 73 | B- | 46,558 |
| 36 | Rancho Palos Verdes Top concern: Total Trihalomethanes (30.8% of limit) | 73 | B- | 38,714 |
| 37 | Compton Top concern: Lead (29.2% of limit) | 72 | B- | 97,140 |
| 38 | Bellflower Top concern: Haloacetic Acids (54.5% of limit) | 71 | B- | 82,227 |
| 39 | Montebello Top concern: Lead (35.3% of limit) | 71 | B- | 65,892 |
| 40 | Gardena Top concern: Total Trihalomethanes (44.1% of limit) | 69 | C+ | 57,874 |
| 41 | Arcadia Top concern: Haloacetic Acids (43.3% of limit) | 68 | C+ | 53,574 |
| 42 | Cerritos Top concern: Total Trihalomethanes (58.6% of limit) | 68 | C+ | 46,952 |
| 43 | Lancaster Top concern: Total Trihalomethanes (74.6% of limit) | 58 | C- | 171,042 |
Top detected contaminants across county water systems
| Contaminant | Avg Level | Max Level | EPA Limit | % of Limit | Cities |
|---|---|---|---|---|---|
| Total Trihalomethanes | 18.592 ug/L | 59.68 ug/L | 80 ug/L | 23.2% | 39 |
| Lead | 0.003 mg/L | 0.009 mg/L | 0.015 mg/L | 18.5% | 37 |
| Haloacetic Acids | 10.898 ug/L | 32.697 ug/L | 60 ug/L | 18.2% | 39 |
| Fluoride | 0.705 mg/L | 1.461 mg/L | 4 mg/L | 17.6% | 40 |
| Copper | 0.218 mg/L | 0.671 mg/L | 1.3 mg/L | 16.8% | 38 |
| Nitrate | 1.348 mg/L | 4.49 mg/L | 10 mg/L | 13.5% | 35 |
| Nitrite | 0.134 mg/L | 0.345 mg/L | 1 mg/L | 13.4% | 37 |
| Arsenic | 0.001 mg/L | 0.005 mg/L | 0.01 mg/L | 12.3% | 38 |
Recent violations across county water systems
Showing 10 of 20 recent violations
Water quality in Los Angeles County, California reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 43 municipal water systems serving a combined population of over 8,042,543 residents.
The county shows strong water quality performance, with scores ranging from 58/100 in Lancaster to 96/100 in Monterey Park. This 38-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across Los Angeles County water systems include Total Trihalomethanes, Lead, Haloacetic Acids. All monitored contaminants remain within acceptable levels relative to EPA Maximum Contaminant Levels (MCLs).
Los Angeles County's water quality is generally good. Residents can feel confident in their tap water quality, though those with specific health concerns or sensitivity to certain contaminants may still benefit from filtration. Regular review of your city's annual Consumer Confidence Report is recommended.
Los Angeles County has an average water quality score of 82/100 (Grade B+) based on analysis of 43 municipal water systems serving 8,042,543 residents.
Monterey Park has the highest water quality score in Los Angeles County at 96/100. View the detailed report for Monterey Park.
Most cities in Los Angeles County have water that meets EPA standards. However, a water filter can provide additional protection and improve taste. The need depends on your specific city and any personal health considerations.
Click on any city in the rankings table above to view its detailed water quality report, including contaminant levels, EPA compliance history, and filter recommendations.