The owner shall connect all applicable plumbing outlets to the public sewer by the construction of a side sewer at his expense at the point designated by the city; provided, however, that the city shall bear the expense of connection to city sewer where hookup is necessitated by the replacement of an existing public sewer serving the property. Such installation and connection, unless otherwise authorized, shall be completed within ninety (90) days after the date of mailing or personal service of notice to the property owner directing such owner to make such connection.