Payment of an estimated water bill does not in any way restrict the right of the municipal water utility to render corrected water bills covering the period of time included in the estimated water bills and to collect the proper amounts as shown by a subsequent reading of the meters, less the amount paid on the estimated water bills by the customer. If the amount paid on estimated water bills exceeds the proper amount as computed for a subsequent reading of the meter or by negotiation, then a proper credit or refund shall be given the customer involved. (Prior code § 33-11)