53 Pa. Stat. § 25896
The city councils of any city of the second class shall, at the expiration of the terms of office of the present board of assessors of said cities, and every third year thereafter, elect five residents of said city as a board of assessors to make, revise or alter assessments of all subjects of taxation for taxation for city purposes, who shall serve for the term of three years from the first Monday of April next ensuing such election, and until their successors shall be duly chosen and qualified; councils shall, at the time of their election, designate one of such assessors as chief assessor, and each of them shall receive such annual salary as may be provided by law. Such assessors shall, immediately after their election, be severally sworn or affirmed to faithfully and impartially perform the duties pertaining to their office. Any vacancy occurring in such board by death, resignation or otherwise shall be filled be such city councils for the unexpired term. Whenever a full board of assessors is to be elected each members of council shall be entitled to vote for not more than four of the members to be elected.
53 P.S. § 25896