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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 5 cities serving 538,863 residents
Contra Costa County in California has an average water quality score of 100/100 (Grade A) based on analysis of 5 municipal water systems. The county's water systems serve approximately 538,863 residents.
Overall, Contra Costa County demonstrates good water quality standards. 5 of 5 cities exceed the county average, with Pittsburg leading with a score of 100/100.
5 cities ranked by water quality score
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) | 17.019 ug/L | 24.154 ug/L | 80 ug/L | 21.3% | 4 |
| Fluoride (2012–2019 avg) | 0.556 mg/L | 0.736 mg/L | 4 mg/L | 13.9% | 3 |
| Nitrate (2012–2019 avg) | 1.234 mg/L | 4.167 mg/L | 10 mg/L | 12.3% | 4 |
| Uranium (2012–2019 avg) | 3.174 ug/L | 3.174 ug/L | 30 ug/L | 10.6% | 1 |
| HAA5 (2012–2019 avg) | 4.506 ug/L | 6.553 ug/L | 60 ug/L | 7.5% | 5 |
| Arsenic (2012–2019 avg) | 0.562 ug/L | 1.687 ug/L | 10 ug/L | 5.6% | 3 |
| Lead (90th percentile) | 0.62 ppb | 3.1 ppb | 15 ppb | 4.1% | 5 |
| PFAS (PFOA/PFOS max, UCMR5) | 0 ppt | 0 ppt | 4 ppt | 0% | 5 |
Water quality in Contra Costa County, California reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 5 municipal water systems serving a combined population of over 538,863 residents.
The county shows strong water quality performance, with scores ranging from 100/100 in Concord to 100/100 in Pittsburg. This 0-point spread indicates relatively consistent water quality standards across municipal systems.
The most prevalent contaminants detected across Contra Costa County water systems include TTHM (2012–2019 avg), Fluoride (2012–2019 avg), Nitrate (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
Contra Costa 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.
Contra Costa County has an average water quality score of 100/100 (Grade A) based on analysis of 5 municipal water systems serving 538,863 residents.
Pittsburg has the highest water quality score in Contra Costa County at 100/100. View the detailed report for Pittsburg.
Most cities in Contra Costa 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.