Loading water data...
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 20 cities serving 2,853,878 residents
Orange County in California has an average water quality score of 89/100 (Grade B) based on analysis of 20 municipal water systems. The county's water systems serve approximately 2,853,878 residents.
Overall, Orange County demonstrates good water quality standards. 10 of 20 cities exceed the county average, with San Clemente leading with a score of 100/100.
20 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Laguna Hills | 100 | A | 170,236 |
| 2 | Rancho Santa Margarita | 100 | A | 168,289 |
| 3 | Costa Mesa | 100 | A | 110,000 |
| 4 | Newport Beach | 100 | A | 68,572 |
| 5 | La Habra | 100 | A | 63,118 |
| 6 | San Clemente | 100 | A | 51,545 |
| 7 | Lake Forest Biggest deduction: Other PFAS detected in UCMR5 sampling: PFBA 6.7 ppt (−2 pts) | 98 | A | 51,800 |
| 8 | Irvine Biggest deduction: Other PFAS detected in UCMR5 sampling: PFPeA 3.8 ppt, PFBA 7.9 ppt (−4 pts) | 96 | A | 444,800 |
| 9 | Yorba Linda Biggest deduction: Other PFAS detected in UCMR5 sampling: PFPeA 5.3 ppt, PFBA 20.6 ppt (−4 pts) | 96 | A | 84,292 |
| 10 | Fountain Valley Biggest deduction: Lead 90th-percentile tap result 6 ppb for 2022-01-01–2024-12-31, below the 15 ppb action level (−3 pts) | 95 | A | 56,747 |
| 11 | Huntington Beach Biggest deduction: PFOS detected at up to 6.1 ppt in UCMR5 sampling (2025-09-16), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 201,000 |
| 12 | Westminster Biggest deduction: PFOS detected at up to 5.3 ppt in UCMR5 sampling (2025-09-16), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 90,911 |
| 13 | Buena Park Biggest deduction: PFOS detected at up to 6.8 ppt in UCMR5 sampling (2025-09-16), at or above EPA's 4 ppt MCL (−10 pts) | 88 | B | 81,998 |
| 14 | Tustin Biggest deduction: PFOS detected at up to 4.2 ppt in UCMR5 sampling (2025-11-20), at or above EPA's 4 ppt MCL (−10 pts) | 86 | B | 66,600 |
| 15 | Santa Ana Biggest deduction: PFOA detected at up to 8.9 ppt in UCMR5 sampling (2026-04-27), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 310,539 |
| 16 | Garden Grove Biggest deduction: PFOA detected at up to 8.1 ppt in UCMR5 sampling (2026-04-27), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 174,226 |
| 17 | Fullerton Biggest deduction: PFOA detected at up to 10.8 ppt in UCMR5 sampling (2026-04-27), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 139,461 |
| 18 | Orange Biggest deduction: PFOA detected at up to 9.3 ppt in UCMR5 sampling (2026-04-27), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 120,770 |
| 19 | Placentia Biggest deduction: PFOA detected at up to 6 ppt in UCMR5 sampling (2025-01-27), at or above EPA's 4 ppt MCL (−10 pts) | 74 | C | 50,381 |
| 20 | Anaheim Biggest deduction: PFOA detected at up to 10.1 ppt in UCMR5 sampling (2026-04-27), at or above EPA's 4 ppt MCL (−10 pts) | 73 | C | 348,593 |
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) | 6.245 ppt | 29 ppt | 4 ppt | 156.1% | 20 |
| TTHM (2012–2019 avg) | 26.226 ug/L | 42.885 ug/L | 80 ug/L | 32.8% | 20 |
| Nitrate (2012–2019 avg) | 1.786 mg/L | 4.821 mg/L | 10 mg/L | 17.9% | 7 |
| HAA5 (2012–2019 avg) | 8.4 ug/L | 17.329 ug/L | 60 ug/L | 14% | 20 |
| Uranium (2012–2019 avg) | 3.801 ug/L | 9.026 ug/L | 30 ug/L | 12.7% | 4 |
| Radium (2012–2019 avg) | 0.502 pCi/L | 0.502 pCi/L | 5 pCi/L | 10% | 1 |
| Fluoride (2012–2019 avg) | 0.359 mg/L | 0.605 mg/L | 4 mg/L | 9% | 4 |
| Arsenic (2012–2019 avg) | 0.633 ug/L | 1.242 ug/L | 10 ug/L | 6.3% | 3 |
Recent violations across county water systems
Health-based: MCL exceeded — Maximum Contaminant Level Violation, E. coli (RTCR) - Revised Total Coliform Rule
11/30/2017
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
6/30/2025
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
3/31/2018
Showing 10 of 13 recent violations
Water quality in Orange County, California reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 20 municipal water systems serving a combined population of over 2,853,878 residents.
The county shows strong water quality performance, with scores ranging from 73/100 in Anaheim to 100/100 in San Clemente. This 27-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across Orange 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.
Orange 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.
Orange County has an average water quality score of 89/100 (Grade B) based on analysis of 20 municipal water systems serving 2,853,878 residents.
San Clemente has the highest water quality score in Orange County at 100/100. View the detailed report for San Clemente.
Most cities in Orange 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.