Water service shall be billed as part of a combined service account, payable in accordance with the following:
(Code of Iowa, Sec. 384.84)
1. Bills Issued. Bills for combined service accounts shall be mailed the last weekday of the month.
2. Bills Payable. Payments shall be due on or before the twentieth day of the following month.
3. Late Payment Penalty. A late payment penalty of one and one-half percent of the outstanding balance shall be assessed for any payments not received by the first business day following the due date.