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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 4 cities serving 694,387 residents
Arapahoe County in Colorado has an average water quality score of 93/100 (Grade A) based on analysis of 4 municipal water systems. The county's water systems serve approximately 694,387 residents.
Overall, Arapahoe County demonstrates good water quality standards. 3 of 4 cities exceed the county average, with Littleton leading with a score of 100/100.
4 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Centennial | 100 | A | 55,000 |
| 2 | Littleton | 100 | A | 48,648 |
| 3 | Aurora Biggest deduction: Other PFAS detected in UCMR5 sampling: PFBS 3.3 ppt, PFPeA 7.2 ppt, PFHxA 5.6 ppt, PFBA 7.8 ppt (−6 pts) | 94 | A | 533,407 |
| 4 | Englewood Biggest deduction: PFOA detected at up to 4 ppt in UCMR5 sampling (2025-04-22), at or above EPA's 4 ppt MCL (−10 pts) | 77 | C | 57,332 |
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) | 2 ppt | 4 ppt | 4 ppt | 50% | 2 |
| TTHM (2012–2019 avg) | 31.376 ug/L | 42.159 ug/L | 80 ug/L | 39.2% | 2 |
| Radium (2012–2019 avg) | 1.5 pCi/L | 2.9 pCi/L | 5 pCi/L | 30% | 2 |
| Lead (90th percentile) | 3.75 ppb | 5 ppb | 15 ppb | 25% | 2 |
| HAA5 (2012–2019 avg) | 12.622 ug/L | 14.73 ug/L | 60 ug/L | 21% | 2 |
| Uranium (2012–2019 avg) | 5.775 ug/L | 8.65 ug/L | 30 ug/L | 19.3% | 2 |
| Fluoride (2012–2019 avg) | 0.674 mg/L | 0.758 mg/L | 4 mg/L | 16.9% | 2 |
| Nitrate (2012–2019 avg) | 1.247 mg/L | 2.194 mg/L | 10 mg/L | 12.5% | 2 |
Recent violations across county water systems
Health-based: MCL exceeded — Maximum Contaminant Level Violation, E. coli (RTCR) - Revised Total Coliform Rule
7/31/2021
Monitoring & reporting — Monitoring of Treatment (SWTR-Filter) - Surface Water Treatment Rule
1/31/2022
Other — Consumer Confidence Report Complete Failure to Report - Consumer Confidence Rule
6/30/2021
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
12/31/2015
Water quality in Arapahoe County, Colorado reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 4 municipal water systems serving a combined population of over 694,387 residents.
The county shows strong water quality performance, with scores ranging from 77/100 in Englewood to 100/100 in Littleton. This 23-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across Arapahoe County water systems include PFAS (PFOA/PFOS max, UCMR5), TTHM (2012–2019 avg), Radium (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
Arapahoe 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.
Arapahoe County has an average water quality score of 93/100 (Grade A) based on analysis of 4 municipal water systems serving 694,387 residents.
Littleton has the highest water quality score in Arapahoe County at 100/100. View the detailed report for Littleton.
Most cities in Arapahoe 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.