The customer, upon approval of his application for sewer service, shall pay to the Maintenance Superintendent a tap fee which shall compensate the Municipality for the expense of processing his application and tapping the sewer main. The Superintendent, in his discretion, may direct the customer to hire a licensed plumber to tap the main. The customer shall then be required to pay the expense of procuring the materials required as well as the services of a licensed plumber and shall pay all other costs of installation. (Ref. 18-503 RS Neb.)