Centralia Water Hardness & Quality Report (2026)

Centralia, Washington, in Lewis County — a Lewis County city adjacent to Chehalis and Napavine in the Chehalis River valley of southwest Washington, one of the largest cities in rural Lewis County — receives its municipal water from the Centralia Water Division, drawing from the Skookumchuck River at Skookumchuck Reservoir (Lewis County) through the Centralia treatment plant.

The extremely soft 15.5 mg/L hardness and very low TDS of 24.1 mg/L make Centralia one of the softest water supplies in the entire USA — the absolute lowest hardness reading in this dataset. The Skookumchuck River drains the Western Cascade Range — Miocene Columbia River Basalt peripheral flows (less soluble than the Columbia Plateau basalts), Cretaceous granodiorite (highly insoluble Sierra-Cascade plutonic arc), and Eocene Ohanapecosh Formation volcanic tuff (insoluble). The entirely insoluble volcanic-plutonic Cascade Range watershed contributes essentially no mineral hardness to the supply.

At 15.5 mg/L, Centralia's water is extremely soft — absolutely no scale forms, soap lathers exceptionally, and appliances maintain peak efficiency indefinitely. No descaling is ever needed. The PFAS level of 1.4 ppt is one of the lowest in this dataset — the Lewis County rural southwest Washington setting has no military AFFF sites and very limited industrial PFAS sources, producing an exceptionally clean supply.