Wash. Rev. Code § 87.56.040
Such action shall be one in rem and personal service of process shall not be required to be made on any interested person: PROVIDED, That the court shall be authorized in proper instances to order issuance and personal service of process specifying such time for appearance as the court shall require, AND PROVIDED FURTHER, That any owner of land within the district or any creditor of the district or their respective attorneys may file with the receiver provided for in this chapter, a written request that his or her name and address be placed on the receiver's mailing list and thereafter the receiver shall mail to such person at his or her given address at least ten days' written notice of all subsequent hearings before the court. Personal service of said notice may be made in any instance in lieu of mailing at the option of the receiver.
RCW 87.56.040