Hawaii water quality
Hawaii has 133 active public water systems (152 on file total), 116 of them graded by TapGraded.
Grade distribution
Biggest water systems
HNL-WINDWARD-PEARL HARBOR
HONOLULU, HI · 631,389 served
WAIPAHU-EWA-WAIANAE
HONOLULU, HI · 217,479 served
WAILUKU
WAILUKU, HI · 74,511 served
JOINT BASE PEARL HARBOR-HICKAM
JBPPH, HI · 65,230 served
MILILANI
HONOLULU, HI · 50,573 served
HILO
HILO, HI · 39,477 served
SCHOFIELD BARRACKS
SCHOFIELD BARRACKS, HI · 37,920 served
LIHUE-KAPAA
LIHUE, HI · 34,854 served
MAKAWAO
WAILUKU, HI · 29,868 served
NORTH KONA
HILO, HI · 29,581 served
Lowest-graded systems
Active, graded systems serving at least 10,000 people, ordered by lowest Tap Grade first.
HNL-WINDWARD-PEARL HARBOR
HONOLULU, HI · 631,389 served
MARINE CORPS BASE HAWAII
KANEOHE BAY, HI · 16,300 served
JOINT BASE PEARL HARBOR-HICKAM
JBPPH, HI · 65,230 served
NORTH KONA
HILO, HI · 29,581 served
WAIPAHU-EWA-WAIANAE
HONOLULU, HI · 217,479 served
WAILUKU
WAILUKU, HI · 74,511 served
MILILANI
HONOLULU, HI · 50,573 served
HILO
HILO, HI · 39,477 served
SCHOFIELD BARRACKS
SCHOFIELD BARRACKS, HI · 37,920 served
LIHUE-KAPAA
LIHUE, HI · 34,854 served
Cities in Hawaii
Source: EPA SDWIS/ECHO · Data as of 2026Q2