§ 94. Water works. In case the city owns and operates a system of municipal water works, the commissioner of public works shall appoint, to hold office during his pleasure, a superintendent of water works, who shall have, under the direction of the commissioner, the supervision, care, management and control of the water department and water-works system of the city. It shall be the duty of the commissioner of public works to see that the city has an abundant supply of pure and wholesome water for public and private use; to devise plans and sources of water supply; to plan and supervise the construction, maintenance and extension of the water system and the distribution of water throughout the city; to protect it from contamination; to prescribe rules and regulations for its use, which, when ratified and approved by the common council, shall have the same force and effect as city ordinances. He shall have power, with the assent of the board of estimate and apportionment, to establish rates of rents to be charged and paid annually for the supply of water or for the benefits resulting therefrom, to be called water rents, which shall be apportioned to the different classes of buildings in the city in reference to their dimensions and the ordinary uses of water for the same, and to different lots, as may be practicable, and from time to time to modify and amend, increase or diminish such rates and to extend them to other descriptions of buildings, lots, establishments and uses. He shall also have power, with like assent, to establish rates for the use of water in buildings, establishments, trades and other purposes in or for which water is consumed beyond the quantity required for ordinary purposes, and may require the same paid to him in advance, at the rates thus established, before permission to use such extra quantity of water shall be given.