Kalihi-Palama Water Hardness & Quality Report (2026)

Kalihi–Palama, Hawaii, a neighborhood area in Honolulu on the island of Oahu — historically one of Honolulu's most working-class and ethnically diverse neighborhoods, home to successive waves of immigrant communities (Filipino, Samoan, Micronesian, Vietnamese, and Latin American), adjacent to Honolulu International Airport, and the home of various cultural and historical sites in the lower Kalihi Valley — draws its municipal water supply from the Koolau Basalt basal aquifer via the Honolulu Board of Water Supply (BWS) Kalihi district. Water hardness in Kalihi–Palama measures 51.5 mg/L — classified as moderately soft.

Kalihi–Palama's moderate softness — slightly harder than Pearl City (32.5 mg/L) — reflects the Honolulu BWS distribution characteristics in the Kalihi–Palama zone. The Honolulu basal aquifer (Koolau Basalt freshwater lens) is recharged by rainfall on the Koolau Range (calcareous-poor tholeiitic ocean island basalt terrain). While the raw basal aquifer water is extremely soft, the Kalihi–Palama urban distribution zone's older Honolulu urban infrastructure (the Kalihi–Palama area includes older 20th-century Honolulu urban mains from the post-1900 Honolulu development era) accumulates some mineral content from the soft source water, producing the moderate 51.5 mg/L at Kalihi–Palama.

With hardness at 51.5 mg/L, Kalihi–Palama residents enjoy moderately soft water. Honolulu Board of Water Supply consistently delivers water meeting all Hawaii DOH and EPA Safe Drinking Water Act requirements.