A.
Bills for metered service shall be rendered at least once each quarter and shall show the readings of the meter at the beginning and end of the period for which the bill is rendered and shall give the dates on which the readings were taken.
B.
When a bill is rendered a second time covering a period for which a bill has been rendered, the period shall be clearly stated on the bill.
C.
Where access to a meter cannot be had, the Department may bill the amount charged for the corresponding quarter of the preceding year or for the period corresponding to that for which access is impossible, and in such cases the amount paid will be treated as a credit, the amount due being determined by the next meter reading. Estimated bills rendered under this subsection will indicate the fact that the same are estimated.
D.
Whenever a meter is placed on any service pipe for which water rent has been paid in advance at flat rate prices, the owner or user shall be credited on his bill at meter rates for the amount paid in advance at the time of placing the meter. The amount paid in advance shall be computed on a per diem basis. After any meter has been so placed, the owner or user shall be subject to all rules, regulations and rates set forth herein with regard to metered service.