Hawaii Water Report Card: Worst Water Systems
The most contaminated public water systems in Hawaii, ranked by PFAS levels, lead, and EPA violations from official EPA data.
Quick Answer
Hawaii Volcanoes Nat.Park has the highest lead at 9 ppb. The tables below rank the worst systems in each category so you can see how your water compares.
Highest Lead Levels in Hawaii
Community water systems in Hawaii with the highest 90th-percentile lead result under the EPA Lead and Copper Rule. The EPA action level is 15 ppb; there is no safe level of lead for children.
| # | Water System | Location | Lead 90th-pctile (ppb) | vs 15 ppb |
|---|---|---|---|---|
| 1 | Hawaii Volcanoes Nat.Park | Hawaii National Park · 4,201 served | 9 | within |
| 2 | Maunaloa-Kaluakoi | Maunaloa · 1,000 served | 7.7 | within |
| 3 | Lower Kula | Wailuku · 3,522 served | 5.3 | within |
| 4 | Marine Corps Base Hawaii | Kaneohe Bay · 16,300 served | 5.1 | within |
| 5 | Upper Kula | Wailuku · 7,686 served | 1.7 | within |
| 6 | Ualapue | Wailuku · 1,119 served | 1 | within |
| 7 | Makawao | Wailuku · 29,868 served | 0.9 | within |
| 8 | Lahaina | Wailuku · 20,065 served | 0.8 | within |
| 9 | Kaunakakai | Wailuku · 3,702 served | 0.8 | within |
| 10 | Pahoa | Hilo · 1,885 served | 0 | within |
| 11 | Pahala | Hilo · 1,226 served | 0 | within |
| 12 | Waiohinu-Naalehu | Hilo · 2,948 served | 0 | within |
Most EPA Violations in Hawaii
Community water systems in Hawaii with the most health-based EPA Safe Drinking Water Act violations on record. A health-based violation means a contaminant exceeded its federal limit or required treatment was not applied.
| # | Water System | Location | Health-based violations |
|---|---|---|---|
| 1 | Maunaloa-Kaluakoi | Maunaloa · 1,000 served | 1 |
| 2 | Lower Kula | Wailuku · 3,522 served | 1 |
| 3 | Hilo | Hilo · 39,477 served | 1 |
| 4 | Pahala | Hilo · 1,226 served | 1 |
| 5 | Makawao | Wailuku · 29,868 served | 1 |
| 6 | Lahaina | Wailuku · 20,065 served | 1 |
How This Report Card Is Built
PFAS rankings use EPA UCMR5 monitoring (2023-2025), showing each system's peak detection above the 4 ppt EPA limit. Lead rankings use the EPA Lead and Copper Rule 90th-percentile tap results. Violation counts come from the EPA Safe Drinking Water Information System (SDWIS) and count health-based violations. Lead and violation lists are limited to community water systems serving 1,000 or more people. Figures are the most severe on record and do not necessarily reflect current treated water.
Frequently Asked Questions
Which Hawaii water system has the highest lead levels?
Hawaii Volcanoes Nat.Park in Hawaii National Park had the highest 90th-percentile lead result in Hawaii under the EPA Lead and Copper Rule at 9 ppb (within the 15 ppb action level).
Which Hawaii water system has the most EPA violations?
Maunaloa-Kaluakoi in Maunaloa has the most health-based EPA Safe Drinking Water Act violations on record in Hawaii, with 1 violations.
Where does the Hawaii water report card data come from?
PFAS figures come from EPA UCMR5 monitoring (2023-2025), lead from the EPA Lead and Copper Rule 90th-percentile tap results, and violations from EPA SDWIS health-based violation records. Figures are the most severe on record and do not necessarily reflect current treated water. Check your exact address at knowyourexposure.com.
What Hawaii Residents Should Do
- Look up your exact address at knowyourexposure.com for your system's data
- See the full Hawaii water quality overview
- If your system is listed, a certified filter (reverse osmosis for PFAS, NSF-53 for lead) reduces exposure at the tap. See the best water filters.