Wash. Rev. Code § 90.40.070
Any water users' association which is organized in conformity with the requirements of the United States under said act of congress, and which under its articles of incorporation is authorized to furnish water only to its stockholders, shall be exempt from the payment of any incorporation tax, and from the payment of any annual franchise tax; but shall be required to pay, as preliminary to its incorporation, only a fee of twenty dollars for the filing and recording of its articles of incorporation and the issuance of certificates of incorporation. Whenever, with the consent of the secretary of the interior of the United States, the stockholders of any such association shall adopt any other form of organization to manage the affairs of such reclamation project in connection with which any such water users' association has been organized, such association may dissolve or disincorporate itself by the procedure and subject to the laws relating to the disincorporation of corporations in this state when such dissolution is authorized by a vote of two-thirds of all the stockholders represented at a meeting of the stockholders called for such purpose.
RCW 90.40.070
Corporations and associations (nonprofit): Title 24 RCW.