The paper presents the results of the research concerning the amount of wastewater influent to the wastewater treatment plant in Sława through sewerage system as well as the amount of wastewater delivered by the sanitation fleet. The research was conducted between January 2013 – Septemper 2017. In this period, the daily wastewater inflow to the wastewater treatment plant and monthly sums of wastewater delivered by the sanitation fleet were evaluated. The average volume of the treated sewage was compared to the designed value. The average measured wastewater inflow in the research period was 1971.1 m³·d^-1 and constituted about 66% of the designed inflow to the wastewater treatment plant. Additionally, the percentage share of wastewater delivered by sanitation fleet was estimated in comparison to total amount of treated wastewater. The seasonal changes concerning the quantity of wastewater delivered be the sanitation fleet, resulting from the touristic characteristic of region was taken into account. The seasonal variation had an influence on increasing the percentage of wastewater from septic tanks, cesspools compared to wastewater from sewerage system. In the summer months (July, August), in the analysed period, the percentage share was from 17.1% to 19.9%. Significantly, the shares of the delivered wastewater by sanitation fleet in the summer period, compared to wastewater amount from the sewerage system, could cause technological problems as well as influence the treatment efficiency.