(1)    Sewer service for residential customers shall be billed on the effective dates and at the volumetric rates per thousand gallons of monthly metered water consumption for each residential customer class as provided in Section 9-9 c based on the average monthly water usage of the most recent December, January, and February. The average monthly water usage of the most recent December, January, and February consumption will be calculated every twelve months. For new customers, for which there is no annual water usage information, the customer shall be billed based on actual water usage per month, or 10,000 gallons of water usage per month, whichever is less.

(2)    Sewer service for residential customers qualifying for the lifeline shall be billed on the effective dates and at the volumetric rates per thousand gallons of monthly metered water consumption for the lifeline customer class as provided in Section 9-9 c based on the average monthly water usage of the most recent December, January, and February. The average monthly water usage of the most recent December, January, and February consumption will be calculated every twelve months. For new customers, for which there is no annual water usage information, the customer shall be billed based on actual water usage per month, or 10,000 gallons of water usage per month, whichever is less.

(3)    Sewer service for all non-residential customers shall be billed on the effective dates and at the volumetric rates per thousand gallons of monthly metered water consumption for each corresponding customer class as provided in Section 9-9 c based on the actual monthly water usage for the corresponding billing month.