Wash. Rev. Code § 36.94.480
A county assuming responsibility for a water system that is not in compliance with state or federal requirements for public drinking water systems, and its agents and employees, are immune from lawsuits or causes of action, based on noncompliance with state or federal requirements for public drinking water systems, which predate the date of assuming responsibility and continue after the date of assuming responsibility, provided that the county has submitted and is complying with a plan and schedule of improvements approved by the department of health. This immunity shall expire on the earlier of the date the plan of improvements is completed or four years from the date of assuming responsibility. This immunity does not apply to intentional injuries, fraud, or bad faith.
RCW 36.94.480
Findings-Intent-1994 c 292: See note following RCW 57.04.050.