Water Quality Report · Updated May 12, 2026
Honolulu Municipal Water System
Honolulu Municipal Water System delivers tap water graded D (64/100) by TapWaterSafety.org. The utility serves approximately 345,000 residents in Honolulu, Hawaii using groundwater from the Pearl Harbor Aquifer. The most significant water quality concerns are: Arsenic significantly above health guideline; Chromium-6 detected. For questions, the utility can be reached at (808) 210-7731.
Is Honolulu tap water safe to drink?
Honolulu Municipal Water System delivers tap water that earns a grade of D (64/100) from TapWaterSafety.org — a below-average rating, with multiple concerns including arsenic significantly above health guideline.
The utility serves 345,000 residents in Honolulu, drawing from groundwater (Pearl Harbor Aquifer) and disinfecting with free chlorine.
Public testing data identifies 18 contaminants in this water above EWG's health-based guidelines, including: Arsenic, Arsenic, Arsenic, Haloacetic Acids (HAA5), Haloacetic Acids (HAA5), Haloacetic Acids (HAA5), Total Trihalomethanes (TTHMs), Total Trihalomethanes (TTHMs), Total Trihalomethanes (TTHMs), Nitrate, Nitrate, Nitrate, Chromium-6 (Hexavalent), Chromium-6 (Hexavalent), Chromium-6 (Hexavalent), Lead, Lead, Lead. For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for Honolulu Municipal Water System.
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.
Contact Honolulu Municipal Water System
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Water Quality Contact
For questions about contaminants, test results, or your Consumer Confidence Report.
Treatment Plant
Recommended water filters for Honolulu
Filters matched to the specific contaminants in this 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.
Score breakdown
This utility's overall score of 64/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). 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 |
| Arsenic Heavy metal |
2.27 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 2022 | 568× over |
| Arsenic Heavy metal |
1.95 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 2023 | 488× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
12.1 ppb | 0.1 | 60 | 60 | — | — | 2023 | 121× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
11.0 ppb | 0.1 | 60 | 60 | — | — | 2024 | 110× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
9.2 ppb | 0.1 | 60 | 60 | — | — | 2022 | 92× over |
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
17.5 ppb | 0.6 | 80 | 100 | — | — | 2023 | 29× over |
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
16.9 ppb | 0.6 | 80 | 100 | — | — | 2022 | 28× over |
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
14.7 ppb | 0.6 | 80 | 100 | — | — | 2024 | 24× over |
| Nitrate Inorganic |
3.13 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 2022 | 22× over |
| Nitrate Inorganic |
2.9 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 2024 | 21× over |
| Nitrate Inorganic |
2.75 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 2023 | 20× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.133 ppb | 0.02 | — | — | — | 0.02 | 2023 | 6.7× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.11 ppb | 0.02 | — | — | — | 0.02 | 2024 | 5.5× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.082 ppb | 0.02 | — | — | — | 0.02 | 2022 | 4.1× over |
| Lead Heavy metal |
0.8 ppb | 0 | 15 | 5 | 10 | 0.2 | 2024 | — |
| Lead Heavy metal |
0.656 ppb | 0 | 15 | 5 | 10 | 0.2 | 2023 | — |
| Lead Heavy metal |
0.572 ppb | 0 | 15 | 5 | 10 | 0.2 | 2022 | — |
| Contaminant | Detected (2024) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
14.7 ppb | 0.6 | 80 | 100 | — | — | 24× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
11.0 ppb | 0.1 | 60 | 60 | — | — | 110× over |
| Lead Heavy metal |
0.8 ppb | 0 | 15 | 5 | 10 | 0.2 | — |
| Arsenic Heavy metal |
2.3 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 575× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.11 ppb | 0.02 | — | — | — | 0.02 | 5.5× over |
| Nitrate Inorganic |
2.9 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 21× over |
| Contaminant | Detected (2023) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
17.5 ppb | 0.6 | 80 | 100 | — | — | 29× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
12.1 ppb | 0.1 | 60 | 60 | — | — | 121× over |
| Lead Heavy metal |
0.656 ppb | 0 | 15 | 5 | 10 | 0.2 | — |
| Arsenic Heavy metal |
1.95 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 488× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.133 ppb | 0.02 | — | — | — | 0.02 | 6.7× over |
| Nitrate Inorganic |
2.75 mg/L | 0.14 | 10 | 11.3 | 11.3 | 10 | 20× over |
| Contaminant | Detected (2022) | EWG | EPA | EU DWD | WHO | CA PHG | Status |
|---|---|---|---|---|---|---|---|
| Total Trihalomethanes (TTHMs) Disinfection byproduct |
16.9 ppb | 0.6 | 80 | 100 | — | — | 28× over |
| Haloacetic Acids (HAA5) Disinfection byproduct |
9.2 ppb | 0.1 | 60 | 60 | — | — | 92× over |
| Lead Heavy metal |
0.572 ppb | 0 | 15 | 5 | 10 | 0.2 | — |
| Arsenic Heavy metal |
2.27 ppb | 0.004 | 10 | 10 | 10 | 0.004 | 568× over |
| Chromium-6 (Hexavalent) Heavy metal |
0.082 ppb | 0.02 | — | — | — | 0.02 | 4.1× over |
| 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 (4th ed.), California OEHHA PHGs, EWG Tap Water Database, and Honolulu Municipal Water System's Consumer Confidence Report.
Honolulu Municipal Water System service area
This water system serves 1 community in Honolulu County, Hawaii. Click any city for its dedicated tap water quality page.
Find the right filter for Honolulu water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.