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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 37 cities serving 7,554,782 residents
Los Angeles County in California has an average water quality score of 86/100 (Grade B) based on analysis of 37 municipal water systems. The county's water systems serve approximately 7,554,782 residents.
Overall, Los Angeles County demonstrates good water quality standards. 20 of 37 cities exceed the county average, with Covina leading with a score of 100/100.
37 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Los Angeles | 100 | A | 3,875,566 |
| 2 | Long Beach | 100 | A | 466,772 |
| 3 | Lancaster | 100 | A | 208,129 |
| 4 | Torrance | 100 | A | 106,183 |
| 5 | Hawthorne | 100 | A | 44,718 |
| 6 | Covina | 100 | A | 33,300 |
| 7 | Rosemead Biggest deduction: 1 monitoring/reporting violation in the last 5 years (−1 pts) | 99 | A | 66,809 |
| 8 | Glendora Biggest deduction: 1 monitoring/reporting violation in the last 5 years (−1 pts) | 99 | A | 49,934 |
| 9 | Pasadena Biggest deduction: Nitrate (as N): 2 of 1836 finished-water samples (2012–2019) above the 10 mg/l MCL (0.1% of samples); max 10.3 mg/l (−3 pts) | 97 | A | 164,344 |
| 10 | Baldwin Park Biggest deduction: Nitrate (as N): 20 of 1041 finished-water samples (2012–2019) above the 10 mg/l MCL (1.9% of samples); max 15 mg/l (−3 pts) | 97 | A | 68,871 |
| 11 | Paramount Biggest deduction: Arsenic: 2 of 564 finished-water samples (2012–2019) above the 10 ug/l MCL (0.4% of samples); max 28 ug/l (−3 pts) | 97 | A | 55,200 |
| 12 | Manhattan Beach Biggest deduction: Lead 90th-percentile tap result 5.4 ppb for 2023-01-01–2025-12-31, below the 15 ppb action level (−3 pts) | 97 | A | 32,697 |
| 13 | Palmdale Biggest deduction: Other PFAS detected in UCMR5 sampling: PFBS 4.5 ppt, PFHxA 6.3 ppt, PFPeA 4.6 ppt (−6 pts) | 94 | A | 126,804 |
| 14 | El Monte Biggest deduction: Other PFAS detected in UCMR5 sampling: PFPeA 5.6 ppt, PFBA 10 ppt (−4 pts) | 93 | A | 248,000 |
| 15 | Burbank Biggest deduction: Other PFAS detected in UCMR5 sampling: PFBA 8.1 ppt, PFHxA 4.4 ppt, PFPeA 10.2 ppt (−6 pts) | 90 | A | 105,603 |
| 16 | Alhambra Biggest deduction: Nitrate (as N): 180 of 2832 finished-water samples (2012–2019) above the 10 mg/l MCL (6.4% of samples); max 14.464 mg/l (−10 pts) | 90 | A | 79,776 |
| 17 | Inglewood Biggest deduction: PFOA detected at up to 4.4 ppt in UCMR5 sampling (2024-11-05), at or above EPA's 4 ppt MCL (−10 pts) | 89 | B | 80,824 |
| 18 | Lakewood Biggest deduction: PFOS detected at up to 18.5 ppt in UCMR5 sampling (2026-05-28), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 66,135 |
| 19 | Arcadia Biggest deduction: PFOS detected at up to 10 ppt in UCMR5 sampling (2024-08-06), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 51,361 |
| 20 | Cerritos Biggest deduction: PFOS detected at up to 4.8 ppt in UCMR5 sampling (2025-02-27), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 47,475 |
| 21 | Santa Monica Biggest deduction: PFOA detected at up to 4.6 ppt in UCMR5 sampling (2024-08-21), at or above EPA's 4 ppt MCL (−10 pts) | 84 | B | 89,947 |
| 22 | Azusa Biggest deduction: PFOA detected at up to 7.7 ppt in UCMR5 sampling (2024-12-02), at or above EPA's 4 ppt MCL (−10 pts) | 78 | C | 110,044 |
| 23 | Compton Biggest deduction: PFOA detected at up to 4.9 ppt in UCMR5 sampling (2024-05-09), at or above EPA's 4 ppt MCL (−10 pts) | 78 | C | 74,877 |
| 24 | Huntington Park Biggest deduction: PFOA detected at up to 5.1 ppt in UCMR5 sampling (2024-10-15), at or above EPA's 4 ppt MCL (−10 pts) | 78 | C | 15,437 |
| 25 | Lynwood Biggest deduction: PFOA detected at up to 7.8 ppt in UCMR5 sampling (2025-06-26), at or above EPA's 4 ppt MCL (−10 pts) | 76 | C | 66,967 |
| 26 | Santa Clarita Biggest deduction: PFOA detected at up to 16.9 ppt in UCMR5 sampling (2024-04-04), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 294,090 |
| 27 | Downey Biggest deduction: PFOA detected at up to 15 ppt in UCMR5 sampling (2025-07-01), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 110,556 |
| 28 | South Gate Biggest deduction: PFOA detected at up to 10 ppt in UCMR5 sampling (2024-01-17), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 76,443 |
| 29 | Norwalk Biggest deduction: PFOA detected at up to 16 ppt in UCMR5 sampling (2024-05-16), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 72,624 |
| 30 | Bellflower Biggest deduction: PFOA detected at up to 16 ppt in UCMR5 sampling (2024-05-16), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 72,624 |
| 31 | Whittier Biggest deduction: PFOA detected at up to 6.3 ppt in UCMR5 sampling (2024-04-18), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 66,045 |
| 32 | La Mirada Biggest deduction: PFOA detected at up to 7 ppt in UCMR5 sampling (2025-08-22), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 56,793 |
| 33 | Montebello Biggest deduction: PFOA detected at up to 16 ppt in UCMR5 sampling (2024-10-09), at or above EPA's 4 ppt MCL (−10 pts) | 73 | C | 26,554 |
| 34 | Pico Rivera Biggest deduction: PFOA detected at up to 16 ppt in UCMR5 sampling (2024-08-28), at or above EPA's 4 ppt MCL (−10 pts) | 72 | C | 40,600 |
| 35 | Glendale Biggest deduction: PFOA detected at up to 14.8 ppt in UCMR5 sampling (2025-07-09), at or above EPA's 4 ppt MCL (−10 pts) | 71 | C | 188,784 |
| 36 | Pomona Biggest deduction: PFOA detected at up to 7.1 ppt in UCMR5 sampling (2024-05-15), at or above EPA's 4 ppt MCL (−10 pts) | 71 | C | 151,713 |
| 37 | Monterey Park Biggest deduction: 1 health-based violation still unresolved with EPA/state (−20 pts) | 65 | D | 62,183 |
Real EPA readings across county water systems (lead: latest 90th percentile; PFAS: UCMR5 2023–2026; others: 2012–2019 averages)
| Contaminant | Avg Level | Max Level | EPA Limit | % of Limit | Cities |
|---|---|---|---|---|---|
| PFAS (PFOA/PFOS max, UCMR5) | 12.532 ppt | 59 ppt | 4 ppt | 313.3% | 37 |
| TTHM (2012–2019 avg) | 21.6 ug/L | 58.115 ug/L | 80 ug/L | 27% | 36 |
| Nitrate (2012–2019 avg) | 2.687 mg/L | 6.375 mg/L | 10 mg/L | 26.9% | 17 |
| Arsenic (2012–2019 avg) | 1.859 ug/L | 5.712 ug/L | 10 ug/L | 18.6% | 12 |
| Radium (2012–2019 avg) | 0.737 pCi/L | 0.737 pCi/L | 5 pCi/L | 14.7% | 1 |
| Uranium (2012–2019 avg) | 3.59 ug/L | 18.76 ug/L | 30 ug/L | 12% | 9 |
| Fluoride (2012–2019 avg) | 0.432 mg/L | 0.744 mg/L | 4 mg/L | 10.8% | 14 |
| HAA5 (2012–2019 avg) | 6.261 ug/L | 15.856 ug/L | 60 ug/L | 10.4% | 36 |
Recent violations across county water systems
Health-based: Treatment technique — LSL Inventory - LEAD AND COPPER RULE REVISIONS
10/16/2024
Health-based: Treatment technique — Treatment Technique (SWTR and GWR) - Groundwater Rule
5/31/2019
Health-based: Treatment technique — Treatment Technique (SWTR and GWR) - Groundwater Rule
8/31/2018
Health-based: Treatment technique — Treatment Technique, Level 2 Assessment (RTCR) - Revised Total Coliform Rule
1/31/2018
Health-based: Treatment technique — Treatment Technique (SWTR and GWR) - Long Term 2 Enhanced Surface Water Treatment Rule
12/31/2017
Health-based: Treatment technique — Treatment Technique (SWTR and GWR) - Groundwater Rule
12/31/2015
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 37 municipal water systems serving a combined population of over 7,554,782 residents.
The county shows strong water quality performance, with scores ranging from 65/100 in Monterey Park to 100/100 in Covina. This 35-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 PFAS (PFOA/PFOS max, UCMR5), TTHM (2012–2019 avg), Nitrate (2012–2019 avg). At least one reading averages above 50% of its EPA limit across the county's systems, worth attention from residents and utilities.
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 86/100 (Grade B) based on analysis of 37 municipal water systems serving 7,554,782 residents.
Covina has the highest water quality score in Los Angeles County at 100/100. View the detailed report for Covina.
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.