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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.
Side-by-side comparison of tap water quality
| Metric | Denver | Phoenix | Better |
|---|---|---|---|
| Overall Score | 74/100 | 70/100 | Denver |
| Grade | B- | B- | - |
| Contaminants Tested | 8 | 9 | - |
| Above EPA Limits | 0 | 0 | Tie |
| EPA Violations (Unresolved) | 0 | 0 | Tie |
| Water Source | surface | surface | - |
| Population Served | 717,347 | 1,608,616 | - |
Side-by-side contaminant levels as percentage of EPA limits
| Contaminant | Denver | Phoenix | EPA Limit | Lower Level |
|---|---|---|---|---|
| Total Trihalomethanes | 27.10 ug/L (33.9% of limit) | 13.38 ug/L (16.7% of limit) | 80.00 ug/L | Phoenix |
| Haloacetic Acids | 11.37 ug/L (18.9% of limit) | 18.46 ug/L (30.8% of limit) | 60.00 ug/L | Denver |
| Arsenic | 0.0015 mg/L (15.0% of limit) | 0.0030 mg/L (29.7% of limit) | 0.010 mg/L | Denver |
| Mercury | 0.0004 mg/L (20.7% of limit) | 0.0005 mg/L (27.3% of limit) | 0.0020 mg/L | Denver |
| Nitrite | 0.249 mg/L (24.9% of limit) | 0.027 mg/L (2.7% of limit) | 1.00 mg/L | Phoenix |
| Copper | 0.024 mg/L (1.9% of limit) | 0.302 mg/L (23.3% of limit) | 1.30 mg/L | Denver |
| Fluoride | 0.647 mg/L (16.2% of limit) | 0.575 mg/L (14.4% of limit) | 4.00 mg/L | Phoenix |
| Chromium | Not tested | 0.011 mg/L (11.4% of limit) | 0.100 mg/L | N/A |
| Lead | 0.0011 mg/L (7.3% of limit) | 0.0006 mg/L (4.1% of limit) | 0.015 mg/L | Phoenix |
Based on contaminants detected in each city
Consider an activated carbon filter or pitcher filter to reduce chlorine and improve taste.
Consider an activated carbon filter or pitcher filter to reduce chlorine and improve taste.
Denver outperforms Phoenix in overall water quality, scoring 74/100 compared to 70/100. This 4-point difference reflects meaningful distinctions in contaminant levels, EPA compliance history, and water infrastructure quality. The gap is driven by differences in source water protection, treatment technology, distribution system age, and the regulatory track record of each city's water utility. Residents in both cities should understand what these scores mean for their daily water use and health.
Denver draws from surface sources serving approximately 717,347 people, while Phoenix relies on surface sources serving about 1,608,616 residents. The type of source water significantly affects the contaminants that must be addressed during treatment. Surface water sources such as rivers and reservoirs are more susceptible to agricultural runoff, microbial contamination, and seasonal turbidity, while groundwater sources may contain naturally occurring minerals like arsenic, radium, or fluoride depending on local geology. Both cities treat their water to meet EPA standards under the Safe Drinking Water Act, but the specific treatment processes and their effectiveness vary based on the challenges posed by each source.
Water quality scores are based on EPA SDWIS (Safe Drinking Water Information System) data, which tracks contaminant testing results, compliance violations, and system characteristics for every public water system in the United States. A higher score indicates fewer detected contaminants, better compliance with federal regulations, and stronger infrastructure. However, no water system is perfect, and conditions can change due to aging pipes, seasonal variations, upstream pollution events, or changes in treatment processes. Regardless of your city's score, monitoring your local utility's annual Consumer Confidence Report and considering point-of-use filtration are prudent steps for protecting your household's water quality.
Denver has better overall water quality with a score of 74/100 (Grade B-). Higher overall quality score (74 vs 70)
Denver's tap water has some concerns with a score of 74/100. Consider using a water filter for additional protection.
Phoenix's tap water has some concerns with a score of 70/100. Consider using a water filter for additional protection.
Water filters can provide additional protection and improve taste regardless of your city's water quality score. Given the scores in this comparison, we particularly recommend filtration for residents of Phoenix.