To supply an Olympic-sized swimming pool with water, the most common source is the municipal water supply, which is then treated and introduced into the compensating tank before being distributed through floor nozzles into the pool. However, the openness of the pool to the surrounding environment and swimmers significantly affects the quality of the water, which deteriorates over time. The water quality in the pool must meet the set requirements, particularly during periods of high usage, so it must be continuously purified and kept hygienically safe for drinking, as it can inadvertently enter the body during swimming. As an Olympic-sized pool is designed for swimming and competition, it must meet the requirements of FINA (Fédération Internationale de Natation) [4], the international governing body for aquatic sports such as swimming, diving, water polo, synchronized swimming, and open water swimming. FINA requires that the water temperature be between 25 and 28 °C, stable during competition, and without significant currents. To ensure the desired water temperature and enable operation of an outdoor pool, it is necessary to predict and calculate water heating, which will be provided using a plate heat exchanger. According to DIN standards 19643-1 [1] and 19643-2 [2] and the Regulation on Sanitary-Technical and Hygienic Conditions for Swimming Pools [3], the pool water must be treated in an appropriate way to meet quality requirements. This thesis describes and calculates a water treatment system for an outdoor Olympic-sized pool, consisting of filtration with glass media, UV disinfection, water heating with a plate heat exchanger, and the use of specific chemical agents for water treatment.