It shall be unlawful for the owner or any other person occupying or having charge of any premises within the city which is located within three hundred feet (300') of a sewer main to dispose of sewage therefrom by any means other than by use of the city sewer system. It shall be unlawful to construct or to continue the use of any other sewage disposal system such as a privy vault, cesspool or septic tank on the property, except by written approval of the city council in cases of undue hardship. (1978 Code § 14-220)