SAWS service areas are established by its permits from state regulatory authorities. The service area for water supply includes most of Bexar County, several suburban municipalities and adjacent parts of the county. In addition to serving its own retail customers, SAWS also provides wholesale water supplies to several smaller utility systems within this area.

A larger and somewhat different area, following natural watersheds, is defined for wastewater collection and treatment. SAWS is the only sewage treatment agency in this area, and it charges a fee to the military bases and suburban cities which maintain their own wastewater collection systems. SAWS also provides collection and treatment services by contract to developments outside its defined service area to avoid unnecessary proliferation of state wastewater discharge permits.

Extensions of SAWS water and sewer systems are accomplished by a combination of direct action by new subdivision developers and expansion of off-site facilities by SAWS. First, subdivision developers are required to install all of the water and sewer facilities within their development projects at their own expense. The design and construction of these facilities must be approved by SAWS, and the facilities are dedicated to the System upon completion. Corresponding extension of off-site mains and expansion of overall system capacity are then financed by the development “impact fees,” which are authorized by state law. These fees are enacted by the San Antonio City Council, and they are based on the estimated average water demand by various kinds of development.

Impact fees are recalculated every five years to finance projected system expansion needs based on updated growth projections. This financing mechanism is designed to ensure that new development “pays its own way,” rather than being subsidized by existing customers.