One effective approach to billing residents for water in this circumstance is to estimate, or more precisely, allocate charges using a fixed formula. Often called RUBS for Ratio Utility Billing Service, this approach is a well-established and a well-accepted method when actual utility metering is impractical.
Many properties with these characteristics use RUBS to recover utility costs. Although utility conservation by tenants is not as significant as in properties where water consumption is actually metered, RUBS does help properties eliminate the unpredictable financial performance that can result when utilities are included in the rent.
With RUBS, utilities can be allocated based on the ratio of apartment sizes, the number of occupants, or a combination of these factors.