Liliha - Kapalama Water Hardness & Quality Report (2026)

The Board of Water Supply (BWS) serves Liliha-Kapalama in Honolulu County, Oahu, Hawaii, providing drinking water to over 1 million residents across the island. Water is sourced from basal groundwater aquifers including the Beretania, Moanalua, and Kalihi shafts and wells in the Kalihi-Kapalama area. No surface reservoirs or rivers are used; treatment involves chlorination at wellheads and pumping stations such as the Beretania Shaft and Kapalama Wells for distribution through the urban pipeline network.

The Koolau Mountain Range serves as the primary recharge area, where precipitation infiltrates volcanic soils into the underlying Honolulu Basal Aquifer. Key formations include the Koolau Basalt (Miocene–Pliocene), a fractured aa and pahoehoe lava series with high porosity, interbedded with volcanic ash and tuff from the Koolau and Waianae volcanic shields. Rainwater passes quickly through this inert volcanic rock without picking up significant dissolved minerals, producing very soft water unlike mainland carbonate aquifers that yield harder supplies.

Soft water in Liliha-Kapalama poses minimal scale risk to appliances, reducing buildup in water heaters, dishwashers, and coffee makers compared to harder regions. Pipes and fixtures experience little mineral deposit, extending lifespan with only basic annual flushing. A water softener is not recommended, as it would introduce unnecessary sodium; instead, a carbon filter is suggested for taste enhancement if chlorine is noticeable. Water quality is excellent, with pH at 7.1, lead levels at 0.001 mg/L well below action limits, and TDS around 36 mg/L per BWS semi-annual reports.