The unfiltered drinking water flows into the filter from the inlet side and then passes through the filter cartridges to the pure water outlet. Thus, foreign particles of > 100 µm in size, subject to the filter element, are retained. Depending on their size and weight, the foreign particles either stick to the filter cartridge or fall straight down where they accumulate at the lowest point of the filter. Due to the growing load of the filter cartridges, the differential pressure between the raw water inlet and the pure water outlet increases. If the differential pressure of 0.8 bar is exceeded at the flow rate of the filter, the filter elements have to be replaced.