Section 69B. The water commissioners, or the selectmen authorized to act as such, in a town establishing a water supply or water distributing system under authority of section thirty-nine A of chapter forty shall have exclusive charge and control of the water department and water system, subject to all lawful by-laws and to such instructions, rules and regulations as the town may from time to time impose by its vote. They may establish fountains and hydrants, may relocate or discontinue the same, may regulate the use of the water and fix and collect just and equitable prices and rates for the use thereof, and shall prescribe the time and manner of payment of such prices and rates. The income of the water works shall be appropriated to defray all operating expenses, interest charges and payments on the principal as they accrue upon any bonds or notes issued for the purpose of a municipal water supply. If in any fiscal year there should be a net surplus remaining after providing for the aforesaid charges for that fiscal year, such surplus, or so much thereof as may be necessary to reimburse the town for moneys theretofore paid on account of its water department, shall be paid into the town treasury. If in any fiscal year there should be a net surplus remaining after providing for the aforesaid charges and for the payment of any such reimbursement in full, such surplus may be appropriated for such new construction, extraordinary maintenance, or repairs, as the water commissioners, or selectmen authorized to act as such, with the approval of the town, may determine upon; and in case a net surplus should remain after payment for such new construction, extraordinary maintenance, or repairs, the water rates shall be reduced proportionately. Said commissioners, or the selectmen authorized to act as such, shall annually, and as often as the town may require, render a report upon the condition of the works under their charge, and an account of their doings, including an account of the receipts and expenditures.

The provisions of this section relative to the powers and duties of the water commissioners, or the selectmen acting as such, shall also apply to the commission, board or person having charge and control of the water department or water system of any city, town, or district established under special law, notwithstanding any contrary provision therein, upon the acceptance of this section by such city, town, or district.