RCW 35.92.200: City may extend water system outside limits—Contracts for outside service.

A city or town may enter into a firm contract with any outside municipality, community, corporation, or person, for furnishing them with water without regard to whether said water shall be considered as surplus or not and regardless of the source from which such water is obtained, which contract may fix the terms upon which the outside distribution systems will be installed and the rates at which and the manner in which payment shall be made for the water supplied or for the service rendered.