The municipal water utility shall require from all applicants for residential service a cash deposit of not less than twenty dollars and from all applicants for other residential service a cash deposit in such amount as shall equal sixty days revenue, as estimated by the municipal water utility, but not less than twenty dollars as a guarantee against the nonpayment of bills for service; except, that if applicant is the legal title owner of real property whose credit is approved by the municipal water utility, the municipal water utility may waive such cash deposits. Such cash deposit minus any unpaid amounts for service rendered the customer shall be returned to the depositor upon the final billing. All cash deposits shall be refunded to the depositor after three years from date of deposit; provided, that satisfactory credit shall have been established by the depositor, in the opinion of the municipal water utility. (Prior code § 33-9)