Equipment and procedure for the separation of solid particles and colloids suspended in liquid with automatic washing system of filtering meshes by means of high pressure water jets generated by a group of mobile spray nozzles, moved vertically by a hydraulic piston controlled by the same washing liquid pressure, operating when the filter is empty of liquid in filtration. The liquid jets are generated by a single nozzles or a group of nozzles, supplied with water through the shaft of the same piston. The nozzles are disposed in such a way to sprinkle the whole surface of the filtering mesh. Feeding the cylinder upper chamber with washing liquid with suitable pressure and flow determines the descending movement of the piston and with it of the nozzle or group of nozzles, mounted at the end of the piston shaft. The velocity of movement of the group of nozzles is regulated, creating in different ways, a resistance to the flow of liquid from the cylinder lower chamber. The upward motion of the plunger to its starting position is obtained by the injection of the liquid, which comes from a pneumatic device or from a dedicated circuit, in the cylinder lower chamber, with the consequent flow of liquid from the superior chamber through the nozzles.