Mass. Gen. Laws ch. 41, § 69

If a town votes under section twenty-one to have its selectmen act as water and sewer boards, water commissioners or sewer commissioners, the selectmen may appoint a suitable person to act as superintendent of the water or sewer department or designate the superintendent of streets so to act if the town has voted to have its selectmen appoint such officer, who, subject to the control of the selectmen, shall have all necessary powers therefor.