53 Pa. Stat. § 22762
The commission shall consist of nine persons, who shall be residents of the city or the county within which such city is located, at least seven of whom shall not be paid city employés, to be appointed by the mayor, subject to the approval of the council, three of whom shall be designated to serve until the first day of January, one thousand nine hundred and twenty-eight, three until the first day of January, one thousand nine hundred and thirty, and three until the first day of January, one thousand nine hundred and thirty-two. Their successors shall be appointed on he expiration of their respective terms to serve six years. Vacancies occurring otherwise than through the expiration of term shall be filled as original appointments are made and for the unexpired term. All members of the commission shall serve, as such, without compensation.
53 P.S. § 22762