We analyzed tap water quality data for hundreds of cities in Hawaii to identify the 25 with the most contaminants exceeding health guidelines. This ranking is based on 2026 data from the EPA and EWG databases.
While all public water systems must meet EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels. The cities below have the widest gap between what's in their water and what's considered safe by modern health standards.
Rankings at a Glance
Wailuku, Hawaii
Wailuku has 16 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Wailuku water report →Lihue, Hawaii
Lihue has 15 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Lihue water report →Kaneohe Bay, Hawaii
Kaneohe Bay has 12 contaminants exceeding EWG health guidelines out of 26 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Kaneohe Bay water report →Holualoa, Hawaii
Holualoa has 12 contaminants exceeding EWG health guidelines out of 19 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Holualoa water report →Honolulu, Hawaii
Honolulu has 11 contaminants exceeding EWG health guidelines out of 26 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Honolulu water report →Kunia, Hawaii
Kunia has 11 contaminants exceeding EWG health guidelines out of 12 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Kunia water report →Waikoloa, Hawaii
Waikoloa has 10 contaminants exceeding EWG health guidelines out of 15 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Waikoloa water report →Makawao, Hawaii
Makawao has 9 contaminants exceeding EWG health guidelines out of 12 total detected, placing it among the most concerning water supplies analyzed.
See full Makawao water report →Jbpph, Hawaii
Jbpph has 8 contaminants exceeding EWG health guidelines out of 13 total detected, placing it among the most concerning water supplies analyzed.
See full Jbpph water report →Schofield Barracks, Hawaii
Schofield Barracks has 8 contaminants exceeding EWG health guidelines out of 12 total detected, placing it among the most concerning water supplies analyzed.
See full Schofield Barracks water report →Maunaloa, Hawaii
Maunaloa has 8 contaminants exceeding EWG health guidelines out of 9 total detected, placing it among the most concerning water supplies analyzed.
See full Maunaloa water report →Kailua Kona, Hawaii
Kailua Kona has 7 contaminants exceeding EWG health guidelines out of 9 total detected, placing it among the most concerning water supplies analyzed.
See full Kailua Kona water report →Lanai City, Hawaii
Lanai City has 7 contaminants exceeding EWG health guidelines out of 8 total detected, placing it among the most concerning water supplies analyzed.
See full Lanai City water report →Laie, Hawaii
Laie has 7 contaminants exceeding EWG health guidelines out of 8 total detected, placing it among the most concerning water supplies analyzed.
See full Laie water report →Kaunakakai, Hawaii
Kaunakakai has 7 contaminants exceeding EWG health guidelines out of 7 total detected, placing it among the most concerning water supplies analyzed.
See full Kaunakakai water report →Kahului, Hawaii
Kahului has 6 contaminants exceeding EWG health guidelines out of 8 total detected, placing it among the most concerning water supplies analyzed.
See full Kahului water report →Hawaii National Park, Hawaii
Hawaii National Park has 6 contaminants exceeding EWG health guidelines out of 8 total detected, placing it among the most concerning water supplies analyzed.
See full Hawaii National Park water report →Pearl City, Hawaii
Pearl City has 6 contaminants exceeding EWG health guidelines out of 7 total detected, placing it among the most concerning water supplies analyzed.
See full Pearl City water report →Kalaupapa, Hawaii
Kalaupapa has 6 contaminants exceeding EWG health guidelines out of 6 total detected, placing it among the most concerning water supplies analyzed.
See full Kalaupapa water report →Kailua-kona, Hawaii
Kailua-kona has 5 contaminants exceeding EWG health guidelines out of 9 total detected, placing it among the most concerning water supplies analyzed.
See full Kailua-kona water report →Beverly Hills, Hawaii
Beverly Hills has 5 contaminants exceeding EWG health guidelines out of 7 total detected, placing it among the most concerning water supplies analyzed.
See full Beverly Hills water report →Pahoa, Hawaii
Pahoa has 5 contaminants exceeding EWG health guidelines out of 6 total detected, placing it among the most concerning water supplies analyzed.
See full Pahoa water report →Pukalani, Hawaii
Pukalani has 4 contaminants exceeding EWG health guidelines out of 7 total detected, placing it among the most concerning water supplies analyzed.
See full Pukalani water report →Kaumakani, Hawaii
Kaumakani has 4 contaminants exceeding EWG health guidelines out of 6 total detected, placing it among the most concerning water supplies analyzed.
See full Kaumakani water report →Kamuela, Hawaii
Kamuela has 4 contaminants exceeding EWG health guidelines out of 4 total detected, placing it among the most concerning water supplies analyzed.
See full Kamuela water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Total trihalomethanes (TTHMs), Bromoform, Nitrate. These appear repeatedly across different water systems and regions.
Water quality varies significantly even within the same state, driven by local geology, agricultural activity, and industrial proximity.
Across all ranked cities, 199 contaminant readings exceed EWG health guidelines, but only 0 exceed EPA legal limits. This gap of 199 highlights how legal standards may not fully protect public health — EPA limits haven't been updated for many contaminants in decades.
Full Rankings Table
| Rank | City | State | Detected | Above Guidelines | Above Legal | People Served |
|---|---|---|---|---|---|---|
| 1 | Wailuku | HI | 25 | 16 | 0 | 74,511 |
| 2 | Lihue | HI | 25 | 15 | 0 | 34,854 |
| 3 | Kaneohe Bay | HI | 26 | 12 | 0 | 16,300 |
| 4 | Holualoa | HI | 19 | 12 | 0 | 250 |
| 5 | Honolulu | HI | 26 | 11 | 0 | 631,389 |
| 6 | Kunia | HI | 12 | 11 | 0 | 650 |
| 7 | Waikoloa | HI | 15 | 10 | 0 | 12,100 |
| 8 | Makawao | HI | 12 | 9 | 0 | 1,200 |
| 9 | Jbpph | HI | 13 | 8 | 0 | 65,230 |
| 10 | Schofield Barracks | HI | 12 | 8 | 0 | 37,920 |
| 11 | Maunaloa | HI | 9 | 8 | 0 | 1,000 |
| 12 | Kailua Kona | HI | 9 | 7 | 0 | 468 |
| 13 | Lanai City | HI | 8 | 7 | 0 | 3,200 |
| 14 | Laie | HI | 8 | 7 | 0 | 0 |
| 15 | Kaunakakai | HI | 7 | 7 | 0 | 2,400 |
| 16 | Kahului | HI | 8 | 6 | 0 | 606 |
| 17 | Hawaii National Park | HI | 8 | 6 | 0 | 0 |
| 18 | Pearl City | HI | 7 | 6 | 0 | 444 |
| 19 | Kalaupapa | HI | 6 | 6 | 0 | 110 |
| 20 | Kailua-kona | HI | 9 | 5 | 0 | 1,945 |
| 21 | Beverly Hills | HI | 7 | 5 | 0 | 100 |
| 22 | Pahoa | HI | 6 | 5 | 0 | 3,546 |
| 23 | Pukalani | HI | 7 | 4 | 0 | 32 |
| 24 | Kaumakani | HI | 6 | 4 | 0 | 1,271 |
| 25 | Kamuela | HI | 4 | 4 | 0 | 850 |
Frequently Asked Questions
What city has the worst tap water in Hawaii?
Based on 2026 data, Wailuku, HI has the most contaminants exceeding EWG health guidelines among the cities we analyzed.
How are cities ranked in this report?
Cities are ranked by the number of contaminants exceeding EWG health guidelines. These guidelines are typically stricter than EPA legal limits and reflect current scientific research on safe exposure levels.
Is my tap water safe if my city isn't on this list?
Not necessarily. Even cities not on this list may have contaminants of concern. We recommend checking your specific water quality using our free water scan tool.
What's the best water filter for contaminated water?
A reverse osmosis (RO) system is the most effective for removing the widest range of contaminants. For whole-home protection, a combination of RO for drinking water and a whole-home filter for showers and baths is recommended.
Related Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: April 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
