The continuous settling of suspended solids inside the filtering cylinder (4) obstructs the passage of water which results in a pressure difference (∆P). At a preset value of ∆P (range 0.3 ÷ 1 Bar) an automatic cycle will start to clean the filter cylinder (4). This operation begins with a signal that opens the discharge valve (3) and creates communication between the suction nozzles (1) with the outside environment. At the same time, the electric motor (5) creates a rotating motion which enables the nozzles to inspect the filtering surface. Dirt is ejected through the discharge valve (3). The cleaning cycle lasts approximately 15 seconds.