'Ewa Beach Water Hardness & Quality Report (2026)

Ewa Beach, Hawaii, in Honolulu County — a Honolulu County community adjacent to Kapolei and Iroquois Point on the south Oahu Ewa Plain — receives its municipal water from the Oahu Board of Water Supply (BWS), drawing from the Pearl Harbor Aquifer (Ewa-Pearl Harbor basin, Honolulu County, south Oahu) through the Ewa Plain production wells.

The very soft 37.5 mg/L hardness and TDS of 99.5 mg/L reflect Oahu's nearly insoluble volcanic basalt aquifer character — consistent with other Oahu supplies (Kaneohe: ~40-50 mg/L). The Pearl Harbor Aquifer at the Ewa Plain is developed in Quaternary High Stand basalt (low-density tholeiitic basalt — very low mineral solubility), Pliocene Ko'olau Basalt (insoluble), and overlying Quaternary marine-carbonate caprock (minor calcareous contribution from the coastal belt). The predominantly insoluble Hawaiian volcanic geology contributes minimal mineral hardness to the supply.

At 37.5 mg/L, Ewa Beach's water is very soft — essentially no scale forms, soap lathers abundantly, and appliances maintain excellent efficiency. Annual descaling is sufficient. The PFAS level of 0.9 ppt is among the lowest in this dataset — Ewa Beach's proximity to the Pearl Harbor Naval Complex is offset by the deep volcanic aquifer source being largely isolated from surface AFFF contamination, producing very clean PFAS readings.