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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 3 cities serving 872,216 residents
Honolulu County in Hawaii has an average water quality score of 99/100 (Grade A) based on analysis of 3 municipal water systems. The county's water systems serve approximately 872,216 residents.
Overall, Honolulu County demonstrates good water quality standards. 1 of 3 cities exceed the county average, with Wahiawa leading with a score of 100/100.
3 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 |
|---|---|---|---|---|---|
| PFAS (PFOA/PFOS max, UCMR5) | 1 ppt | 3 ppt | 4 ppt | 25% | 3 |
| Nitrate (2012–2019 avg) | 1.516 mg/L | 2.432 mg/L | 10 mg/L | 15.2% | 3 |
| Fluoride (2012–2019 avg) | 0.082 mg/L | 0.154 mg/L | 4 mg/L | 2.1% | 3 |
| TTHM (2012–2019 avg) | 1.261 ug/L | 1.778 ug/L | 80 ug/L | 1.6% | 3 |
| Arsenic (2012–2019 avg) | 0.008 ug/L | 0.023 ug/L | 10 ug/L | 0.1% | 3 |
| Lead (90th percentile) | 0 ppb | 0 ppb | 15 ppb | 0% | 3 |
| HAA5 (2012–2019 avg) | 0.011 ug/L | 0.034 ug/L | 60 ug/L | 0% | 3 |
| Radium (2012–2019 avg) | 0 pCi/L | 0 pCi/L | 5 pCi/L | 0% | 3 |
Water quality in Honolulu County, Hawaii reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 3 municipal water systems serving a combined population of over 872,216 residents.
The county shows strong water quality performance, with scores ranging from 98/100 in Honolulu to 100/100 in Wahiawa. This 2-point spread indicates relatively consistent water quality standards across municipal systems.
The most prevalent contaminants detected across Honolulu County water systems include PFAS (PFOA/PFOS max, UCMR5), Nitrate (2012–2019 avg), Fluoride (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
Honolulu 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.
Honolulu County has an average water quality score of 99/100 (Grade A) based on analysis of 3 municipal water systems serving 872,216 residents.
Wahiawa has the highest water quality score in Honolulu County at 100/100. View the detailed report for Wahiawa.
Most cities in Honolulu 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.