The design of buried underground flexible pipes proposed in domestic standards does not properly reflect changes in ground characteristics. Overseas standards suggest that pipe deflection must be considered while designing them. Therefore, in this study, the structural behavior of underground polyvinyl chloride pipes was investigated through experiments and the finite element analysis. In addition, when the pipe deflection occurred at 3% and 5%, the hydraulic characteristics of the polyvinyl chloride pipe showed a slight difference compared to the round pipe.