The patented design of the PP swith-step filter is characterised by optimal efficiency and low maintenance costs. Unlike other self-cleaning filters, the PP step filter operates with a collecting function, achieving an efficiency of 100% during light rainfall of up to 0.6 mm within 5 minutes. As these light rainfall events account for approximately 97% of the annual precipitation, the effective overall efficiency is around 98%. Heavy rainfall events exceeding 0.6 mm within 5 minutes, which occur only 4 to 10 times per year, contribute just 3% to the total precipitation and are used to activate the self-cleaning function. Due to their high, short-term energy input, these rainfall events are ideal for the cleaning process.