There is created a special fund of the city to be known as the “sewer revenue fund.” Any and all connection charges and revenues received for the use of sewers as set forth herein, for sewage disposal service, from the sale of by-products from the sewer treatment plant or from any other source of rental, use or services rendered by such utility shall be credited to and paid into such fund. All engineering expenses incurred by the engineering department in planning, designing, supervising and administering any work on the Everett municipal sewer system, and all expenses of maintenance and operation of the sewer system and sewer department, including but not limited to all improvements, additions, betterments, extensions, repairs, replacements, except when the same are financed by the issuance of bonds, and amounts required to pay and secure the payment of principal and interest on sewer revenue bonds and coupon warrants, shall be paid out of the fund. (Prior code § 14.12.050.)