Our paper analyzed the hydraulic aspects of a rainwater-collecting pipe operation in the conditions of rainfall events calculated using two different models. Model I is recommended for use across the entire country, while model II has a more local character. The dimensions of the collecting pipe were determined in two variants, depending on the employed rainfall model. Finally, the hydraulic capacity of the channel was verified under different conditions of rainwater volume. The investigated area is located in the southeastern part of Krakow, a city in southern Poland. The study covered a catchment area of 9,000 m². The calculation outcomes indicate that the design rainfall intensity determined in model II was higher for the time interval recommended for the drainage system design than in model I. The numerical calculations performed in the storm water management model (SWMM) program, showed that the collecting pipe design based on rainfall intensity from model II was capable of intercepting the design runoff volume, offering storage volume over a substantial length of pipe.