Kihei Water Hardness & Quality Report (2026)

Kihei, Hawaii, in Maui County — a rapidly growing resort and residential community on the sunny southwestern (leeward) coast of Maui facing Maalaea Bay, one of Hawaii's fastest-growing towns, renowned for its beaches (Kamaole Beach Parks), the South Maui resort corridor, and year-round sunny weather — receives its municipal water from the Maui Department of Water Supply (MDWS), which draws from the Haleakala shield volcano's basal and dike-impounded groundwater systems through production wells on the leeward South Maui slope.

The very soft 22 mg/L hardness and very low TDS of 52.3 mg/L reflect Maui's unique Hawaiian shield volcano aquifer character — one of the softest water supplies in the US. The Haleakala volcano (East Maui shield, rising to 10,023 feet) is composed of Pliocene-Pleistocene Hawaiian tholeiitic and alkalic basalt lava flows. Hawaiian shield volcano aquifers are of two types: basal groundwater (freshwater floating on saline water in the volcanic rock at sea level, accessed by shallow wells) and dike-impounded groundwater (rainwater trapped by vertical dike intrusions high in the volcanic pile). The East Maui Irrigation (EMI) system and the MDWS draw from these Haleakala lava flow aquifer systems. Hawaiian basalt is a mafic igneous rock with minimal carbonate content — calcium feldspar (anorthite) and pyroxene dissolve very slowly — producing characteristically very soft, low-mineral Hawaiian groundwater.

At 22 mg/L with TDS 52 mg/L, Kihei's water is very soft — essentially mineral-free by continental US standards. Scale never forms, soap lathers richly, and appliances last their full mechanical lifespan without mineral issues. Annual descaling is more than adequate. The PFAS level of 0.7 ppt is the lowest in this entire dataset and among the lowest documented municipal water PFAS readings in the US — Kihei's isolated Pacific Ocean location, the pristine Haleakala volcano rainwater recharge, the absence of major military airfields or fluorochemical manufacturing in Maui County, and the deep Hawaiian basalt aquifer's natural filtration all contribute to this remarkably clean water reading.