Bills to customers of the municipal utilities, including owners or occupants of premises which are connected to the city sewer system, shall be mailed on the first day of each month or as soon thereafter as may be practicable, and the bills shall be due immediately, and shall be classed as delinquent if not paid on or before the fifteenth day of the month and shall then be subject to collection in any manner provided by law for the collection of debts due the city.
(1973 Code, § 16-7)