(a) The owner or operator of a building containing residential units may install equipment or use an economic allocation methodology to determine the quantity of water that is provided to the tenants and used in the common areas of such a building; and the owner of such a building may charge tenants separately for water and waste-water service based on usage as determined through the use of such equipment or allocation methodology. The activities described in this Code section shall not cause any owner or operator engaging in such activities to be considered the owner or operator of a public water system or a public utility, notwithstanding any provision of law to the contrary.

(b) The owner or operator of a building containing residential units may charge tenants separately for water and waste-water service, provided that the total amount of the charges to the tenants of such a building shall not exceed the total charges paid by the owner or operator for water and waste-water service for such building plus a reasonable fee for establishing, servicing, and billing for water and waste-water service and provided, further, that the terms of the charges are disclosed to the tenants prior to any contractual agreement.