See RCW 59.18.150. That statute, in part, provides,
Quote Quoting RCW 59.18.150 -Landlord's right of entry — Purposes — Searches by fire officials — Conditions.
(1) The tenant shall not unreasonably withhold consent to the landlord to enter into the dwelling unit in order to inspect the premises, make necessary or agreed repairs, alterations, or improvements, supply necessary or agreed services, or exhibit the dwelling unit to prospective or actual purchasers, mortgagees, tenants, workers, or contractors.

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(5) The landlord shall not abuse the right of access or use it to harass the tenant. Except in the case of emergency or if it is impracticable to do so, the landlord shall give the tenant at least two days' notice of his or her intent to enter and shall enter only at reasonable times. The tenant shall not unreasonably withhold consent to the landlord to enter the dwelling unit at a specified time where the landlord has given at least one day's notice of intent to enter to exhibit the dwelling unit to prospective or actual purchasers or tenants. A landlord shall not unreasonably interfere with a tenant's enjoyment of the rented dwelling unit by excessively exhibiting the dwelling unit.