In response to the urgent need for sustainable energy solutions worldwide and the increased adoption in geographically constrained regions, this study explores the hydroelectricity potential in Singapore’s Sewage System. Despite Singapore's limited effective land area and the absence of natural rivers, which generally limit the potential for tidal and traditional hydropower, the country's tropical climate and consistent rainfall ensure a steady water flow through its drainage systems. This unique setting presents an ideal opportunity for innovative hydroelectric generation. POWER DRAIN aims to harness this kinetic energy to generate renewable electricity by installing modified versions of the turbines in the Deep Tunnel Sewerage System (DTSS). Among various water turbines like Kaplan, Francis, and Pelton wheels, the Francis turbine was selected for its centripetal flow operation, ideal for achieving up to 95% energy conversion efficiency in medium-head applications. The vortex chamber’s natural spiral flow, post-sewer exit, allows for the seamless integration of the Francis turbine, maintaining structural integrity. Its suitability for medium-head applications, particularly within the 35 to 50-m depth of the vortex chamber, further underscores its selection. The simulation analysis reveals that the modified version of the Francis turbine is able to generate 25.1 MWh of Mechanical Power and net 23.9 MWh of useful electrical power per unit per day. Maximizing the scale of the project by installing one turbine in each of the approximately 30 vortex chambers across the island is estimated to generate 8.71 GWh of useful electrical power per turbine per year, powering up to 21,775 households (approximately 400 kWh per household). According to our economic analysis, the breakeven point to cover the initial costs would be reached in less than two years of operation, and this project is expected to achieve consistent annual cost savings of $390,339,150, after accounting for recurring costs such as maintenance fees.