Hawaii Tap Water Quality
Check a Hawaii ZIP Code
Overview
Hawaii's municipal water is naturally exceptional: rain filtered through volcanic rock into basal aquifers, so pure that Honolulu's Board of Water Supply delivers it with disinfection alone, no filtration needed. Neighbor-island county systems are similarly clean.
That purity made the 2021 Red Hill crisis a statewide shock: jet fuel from the Navy's underground storage tanks contaminated the base's Pearl Harbor-area system and threatened Oahu's primary aquifer, forcing well shutdowns that still constrain supply. The tanks have since been defueled and closure is underway; municipal wells are monitored and remain unaffected.
Common Contaminants in Hawaii
The 2021 fuel release contaminated the Navy's own system, not BWS municipal wells; ongoing monitoring guards the aquifer and shut wells reduce supply flexibility
Traces of historic plantation fumigants (TCP, EDB) appear in some central Oahu and Maui wells, treated with carbon where present
Some coastal wells trend brackish; managed through blending
Violations & Compliance
County water systems consistently meet all federal standards. The Red Hill contamination occurred on the Navy's separate system; its aftermath is managed as a federal cleanup with independent aquifer monitoring.
Water Hardness in Hawaii
Moderate, typically 50–150 mg/L. Volcanic-aquifer groundwater across the islands is soft to moderately hard, with Honolulu's supply in the moderate range.
Hardness affects taste, limescale, and soap — not safety. Compare levels across all cities or read the water hardness guide.
City Water Reports in Hawaii
Frequently Asked Questions
Sources & References
The safety rating and guidance on this page draw on the following sources. See our full methodology.
- •US EPA Safe Drinking Water Act regulations
- •EWG Tap Water Database
- •The utility's most recent Consumer Confidence Report (CCR)
- •WHO Guidelines for Drinking-water Quality