Inflow and infiltration (I&I) is an unavoidable problem which affects underground infrastructures such as water mains, sewer lines, and storm water systems. The additional water and intruded debris, due to I&I, can hinder the flow capacity of the pipe network. However, with proper management, such problems can be minimized or controlled. By using a qualitative approach to determine the areas susceptible to I&I, application of geographic information system (GIS) can minimize cost and time. The results found can highlight the most I&I vulnerable areas, which can be used for underground infrastructure management. In this study, maps of Youngstown’s sewer lines and surrounding areas were generated and used. Pipe age, an empirical operating coefficient, sewer classifications, and soil hydraulics were the parameters used to identify each pipe segments. The results of this study show that majority of pipelines from downtown and south side of the city were determined to be in very poor conditions. The method used in this study reduces the scale of work, by generating a map, indicating areas with highest susceptibility.