There is hereby created a fund to be designated as "City of Princeton Sanitary Board Revenue Account," into which account shall be placed and deposited all funds derived from the issuance of permits under Section 921.16 and 921.17 of the Streets, Utilities and Public Services Code and all funds derived from tap fees and rates or charges for service to the users of the system under and by virtue of Article 925 as well as of miscellaneous receipts from whatever sources derived. All expenses of maintenance and operation of such system or works, including the salaries of all officers and employees of the Sanitary Board as such and cost incurred in tapping shall be paid out of the fund, and the Sanitary Board may from time to time spend out of such funds so much thereof as they may deem proper for new construction and extensions of the sewer system or works. The Sanitary Board shall from time to time make transfers from the fund to the fund designated "City of Princeton Sanitary Board Bond Fund Account" as may be deemed proper. (1975 Code Sec. 15-21)