It shall be the duty of the judges of the court of common pleas, upon application of any incorporated town or borough council, as aforesaid, to appoint such commissioners of water-works, one of whom shall be appointed to serve for one year, one for two years, and one for three years; and annually thereafter the judges of said court shall appoint one citizen to serve as a commissioner of water-works, for a term of three years. In case of a vacancy the said court shall fill the same for the unexpired term thereof. Such commissioners of water-works shall not receive salary for their services, but shall be paid all such sums necessarily expended in the performance of their duty: Provided, however, That after three years from the first appointment under this act, the borough or town council may at any time rescind the resolution asking for the appointment of a commissioner of water-works. When such resolution shall be so rescinded the court shall make no further appointment of commissioner of water-works until a resolution shall again be passed by council asking for such appointment.