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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 11 cities serving 2,734,270 residents
San Diego County in California has an average water quality score of 97/100 (Grade A) based on analysis of 11 municipal water systems. The county's water systems serve approximately 2,734,270 residents.
Overall, San Diego County demonstrates good water quality standards. 10 of 11 cities exceed the county average, with Poway leading with a score of 100/100.
11 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | San Diego | 100 | A | 1,385,379 |
| 2 | La Mesa | 100 | A | 277,668 |
| 3 | Oceanside | 100 | A | 171,483 |
| 4 | Escondido | 100 | A | 137,044 |
| 5 | Vista | 100 | A | 132,430 |
| 6 | Carlsbad | 100 | A | 95,158 |
| 7 | Encinitas | 100 | A | 86,458 |
| 8 | Poway | 100 | A | 49,888 |
| 9 | San Marcos Biggest deduction: 1 monitoring/reporting violation in the last 5 years (−1 pts) | 99 | A | 113,500 |
| 10 | Santee Biggest deduction: Other PFAS detected in UCMR5 sampling: PFBA 5.8 ppt (−2 pts) | 98 | A | 93,980 |
| 11 | Chula Vista Biggest deduction: PFOA detected at up to 11.4 ppt in UCMR5 sampling (2025-07-17), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 191,282 |
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 |
|---|---|---|---|---|---|
| TTHM (2012–2019 avg) | 33.824 ug/L | 46.418 ug/L | 80 ug/L | 42.3% | 11 |
| PFAS (PFOA/PFOS max, UCMR5) | 1.036 ppt | 11.4 ppt | 4 ppt | 25.9% | 11 |
| HAA5 (2012–2019 avg) | 11.873 ug/L | 19.036 ug/L | 60 ug/L | 19.8% | 11 |
| Fluoride (2012–2019 avg) | 0.512 mg/L | 0.698 mg/L | 4 mg/L | 12.8% | 6 |
| Uranium (2012–2019 avg) | 3.401 ug/L | 5.792 ug/L | 30 ug/L | 11.3% | 5 |
| Arsenic (2012–2019 avg) | 0.543 ug/L | 2.613 ug/L | 10 ug/L | 5.4% | 6 |
| Nitrate (2012–2019 avg) | 0.369 mg/L | 2.092 mg/L | 10 mg/L | 3.7% | 6 |
| Lead (90th percentile) | 0.2 ppb | 1.1 ppb | 15 ppb | 1.3% | 11 |
Recent violations across county water systems
Water quality in San Diego County, California reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 11 municipal water systems serving a combined population of over 2,734,270 residents.
The county shows strong water quality performance, with scores ranging from 74/100 in Chula Vista to 100/100 in Poway. This 26-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across San Diego County water systems include TTHM (2012–2019 avg), PFAS (PFOA/PFOS max, UCMR5), HAA5 (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
San Diego 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.
San Diego County has an average water quality score of 97/100 (Grade A) based on analysis of 11 municipal water systems serving 2,734,270 residents.
Poway has the highest water quality score in San Diego County at 100/100. View the detailed report for Poway.
Most cities in San Diego 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.