Swimming pool water must undergo treatment, in order to remain clear and clean, free from harmful substances, bacteria, viruses, algae and other pathogens and suitable for use by swimmers. It is treated by means of various purification steps. The water is first transported from swimming pools to a water purification plant. In the water purification plant, it will flow through a hair removal filter, which removes raw pollutions, such as hairs, plasters and leaves, from water. After that, a flocculant is added, which causes smaller colloids to bind together. The parameters that indicate the presence of undissolved particles are water turbidity and potassium permanganate demand of the water. Potassium permanganate is used as an indicator of organic matter oxidation. Floating particles are removed from water in a sandfilter. The sandfilter is backflushed periodically. Finally, pollutants are discharged into the sewer.