Wash. Rev. Code § 41.14.130
Whenever a position in the classified service becomes vacant, the appointing power, if it desires to fill the vacancy, shall requisition the commission for the names and addresses of persons eligible for appointment thereto. Before a requisition can be made, the appointing authority shall give employees of the appointing authority who are in layoff status or who have been notified of an intended layoff an opportunity to qualify for any class within the office of the appointing authority. The commission shall certify the names of the five persons highest on the eligible list for the class to which the vacant position has been allocated, who are willing to accept employment. If there is no appropriate eligible list for the class, the commission shall certify the names of the five persons standing highest on the list held appropriate for such class. If more than one vacancy is to be filled an additional name shall be certified for each additional vacancy. The appointing power shall forthwith appoint a person from those certified to the vacant position.
To enable the appointing power to exercise a greater degree of choice in the filling of positions, no appointment, employment, or promotion in any position in the classified service shall be deemed complete until after the expiration of a period of one year's probationary service, as may be provided in the rules of the civil service commission, during which the appointing power may terminate the employment of the person appointed, if during the performance test thus afforded, upon observation or consideration of the performance of duty, the appointing power deems such person unfit or unsatisfactory for service in the office of county sheriff. Thereupon the appointing power shall again requisition the commission for the names and addresses of persons eligible for appointment in the manner provided by this section and the person appointed in the manner provided by this section shall likewise enter upon said duties for the probationary period, until some person is found who is deemed fit for appointment, employment, or promotion whereupon the appointment, employment, or promotion shall be deemed complete.
RCW 41.14.130