Wash. Rev. Code § 35.67.310
Every city or town may permit connections with any of its sewers, either directly or indirectly, from property beyond its limits, upon such terms, conditions and payments as may be prescribed by ordinance, which may be required by the city or town to be evidenced by a written agreement between the city or town and the owner of the property to be served by the connecting sewer.
If any such agreement is made and filed with the county auditor of the county in which said property is located, it shall constitute a covenant running with the land and the agreements and covenants therein shall be binding on the owner and all persons subsequently acquiring any right, title or interest in or to said property.
If the terms and conditions of the ordinance or of the agreement are not kept and performed, or the payments made, as required, the city or town may disconnect the sewer and for that purpose may at any time enter upon any public street or road or upon said property.
RCW 35.67.310