It is unlawful for any person to connect any drain or sewer pipe with the city sewer system unless the person is a duly licensed plumber or unless, in the absence of a duly licensed plumber, any proposed connection to, alteration of, or change of connection to the sewer system shall be first submitted to the sewer superintendent for review and approval. After such approval, the installation or work done shall be subject to inspection by the superintendent or his or her agent. (Prior code § 14-221)