Aim of the study:
The aim of the paper was to analyze the influence of atmospheric precipitation on the variability of wastewater outflow from a selected sewerage system in southern Poland. The research period was the years 2011-2016. The daily outflows of wastewater from the sewerage system were used.

Material and methods:
Rainfall data were obtained from a station located 7 km away from the tested facility (the nearest rainfall measurement station from the tested object) and based on this data, were determined the average daily precipitation values for the examined period. Subsequently, the research period was divided by the amount of precipitation into 7 basic groups. It was determined whether the average values of wastewater outflow from the sewerage system in particular groups of rainfall intensity significantly differ from each other.

Results and conclusions:
Based on the results of the research were proposed actions aimed at increasing the control of accidental water outflow to the sewerage system. It has been determined the operations minimizing the inflow of accidental rainwaters on, particularly sensitive sewerage system sections. Educational training should be introduced in the commune (agglomeration) regarding the management of rainwater so as to stop them as much as possible at the place where they arise.