The mayor and board of aldermen may, for the purpose of arriving at the quantity of water used by any consumer, and for the purpose of establishing either a flat rate or a rate by measure for any such consumer, install and connect a meter to the water mains on the premises of any water consumer for such period of time as they shall think proper, and require any such consumer to pay either for measured water or at a flat rate such charges as shall be prescribed by the board of aldermen. (Code 1953, § 21.9.)