Liability for sewer service shall begin, as to all users now connected with the sewage system of the City, on April 15, 1974; and thereafter liability for sewer service shall begin as to each subsequent user on the date of connection to the sewage system; and such liability shall continue thereafter unless the premises served thereby are disconnected from the sewage system with the approval of the Sanitary Board. After such liability begins no allowance shall be made for vacant houses unless request in writing to have the premises disconnected from the sewage system is received by the Board, nor will any allowance be made for any disconnection period which is less than thirty days. (1978 Code Sec. 23-14.)