Constant deposit of suspended solid particles inside the filtering cylinder (1) obstructs the passage of water, causing a pressure differential (∆P). At a preset ∆P value (ranging from 0.2 ÷ 0.4 Bar) an automatic cleaning cycle of the filtering (1) cylinder starts. This activity begins with a signal that opens the discharge valve (2) allowing communication of the suction nozzles (3) with the outside environment. At the same time, the electric motor’s (4) rotary motion allows the nozzles to inspect the entire filtering surface. Dirt is removed through the discharge valve (2). The cleaning cycle lasts 15 sec.