Wash. Rev. Code § 2.08.160
In any county where there shall be more than one superior judge, or in which a superior judge of another county may be holding a session of the superior court, as provided in RCW 2.08.140 through 2.08.170, there may be as many sessions of the superior court at the same time as there are judges thereof, or assigned to duty therein by the governor, or responding to a request made as provided in RCW 2.08.150. In such cases the business of the court shall be so distributed and assigned by law, or in the absence of legislation therefor, by such rules and orders of the court as shall best promote and secure the convenient and expeditious transaction thereof. Judgments, decrees, orders and proceedings of any session of the superior court held by one or more of the judges of said court, or by any judge of the superior court of another county pursuant to the provisions of RCW 2.08.140 through 2.08.170, shall be equally effectual as if all the judges of such court presided at such session.
RCW 2.08.160