Effective management and expansion of sewer networks are vital for sustainable urban development and environmental protection. Traditional approaches, often reliant on manual surveys and assessments, suffer from inefficiencies, high labor costs, and delayed decision-making. This study introduces an advanced Geospatial Information Systems (GIS) framework that not only revolutionizes operational workflows but also contributes to increased revenue through expedited connection allocations and reduced maintenance costs. In the cities of Isfahan and Khomeinishahr, the proposed methodology integrates multiple data layers—including detailed sewer infrastructure (treatment plants, manholes, collection pipelines, and pumping stations), comprehensive subscriber databases, and cadastral records—to perform high-resolution spatial analyses. The process involves systematic steps such as descriptive data extraction, GIS data synchronization, precise distance calculations from existing sewer lines, and classification of subscribers into prioritized groups (e.g., within 8 meters for immediate connection, 8–20 meters for network extension, and beyond 20 meters for network redesign). Field validation confirms an accuracy rate of approximately 95%, while the overall planning time is reduced. Additionally, by automating the identification of unconnected subscribers, this GIS-based solution accelerates revenue generation through faster connection sales and more efficient resource allocation. Beyond immediate operational benefits, transitioning from localized septic systems to centralized sewer networks significantly mitigates environmental risks—reducing soil and groundwater contamination and promoting long-term sustainability. Overall, the results demonstrate that the enriched GIS approach not only enhances the precision of urban sewer management but also lays a scalable framework for future smart infrastructure initiatives, combining enhanced operational efficiency with tangible economic and environmental benefits.