Wash. Rev. Code § 59.18.300
It shall be unlawful for a landlord to intentionally cause termination of any of his or her tenant's utility services, including water, heat, electricity, or gas, except for an interruption of utility services for a reasonable time in order to make necessary repairs. Any landlord who violates this section may be liable to such tenant for his or her actual damages sustained by him or her, and up to one hundred dollars for each day or part thereof the tenant is thereby deprived of any utility service, and the prevailing party may recover his or her costs of suit or arbitration and a reasonable attorney's fee. It shall be unlawful for a tenant to intentionally cause the loss of utility services provided by the landlord, including water, heat, electricity, or gas, excepting as resulting from the normal occupancy of the premises.
RCW 59.18.300