Tap Water Quality Report
Tap water quality in Honolulu, Hawaii
Tap water in Honolulu, Hawaii receives a grade of D (64/100) from TapWaterSafety.org. It's served by Honolulu Municipal Water System. The most significant water quality concerns are: Arsenic significantly above health guideline; Chromium-6 detected. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database, and Honolulu's published Consumer Confidence Report.
What's in Honolulu's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving Honolulu.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 2.3 ppb, 575x above the EWG health guideline of 0.004 ppb.
Chromium-6 detected
Moderate concernChromium-6 detected at 0.11 ppb.
Recommended filters for Honolulu
Filters matched to the specific contaminants in Honolulu's water supply.
Reverse Osmosis
$249-$750Arsenic is most effectively removed by reverse osmosis. Some specialized adsorptive filters also work.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in Honolulu's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Arsenic Heavy metal |
2.3 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 2024 | 575× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
12.1 ppb | 0.1 | 60 | 60 | — | — | 2023 | 121× over |
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
17.5 ppb | 0.6 | 80 | 100 | — | — | 2023 | 29× over |
| Nitrate Inorganic |
3.13 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 2022 | 22× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.133 ppb | 0.02 | — | — | — | 0.02 | 2023 | 6.7× over |
| Lead Heavy metal |
0.8 ppb | 0 | 15 | 5 | 10 | 0.2 | 2024 | — |
| Contaminant | Detected (2024) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Arsenic Heavy metal |
2.3 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 575× over |
| Lead Heavy metal |
0.8 ppb | 0 | 15 | 5 | 10 | 0.2 | — |
| Contaminant | Detected (2023) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Haloacetic Acids (HAA5) Disinfection byproduct |
12.1 ppb | 0.1 | 60 | 60 | — | — | 121× over |
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
17.5 ppb | 0.6 | 80 | 100 | — | — | 29× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.133 ppb | 0.02 | — | — | — | 0.02 | 6.7× over |
| Contaminant | Detected (2022) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Nitrate Inorganic |
3.13 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 22× over |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from Honolulu Municipal Water System.
General Contact
Water Quality Contact
For questions about contaminants or test results.