Abstract: The filter has a filtering chamber in which a number of hollow filtering elements are arranged on a circle about the axis of the filter. The chamber has a liquid inlet and a liquid outlet and the hollow filtering elements communicate in parallel with the inlet and outlet. A hollow arm defining a passageway is rotatable about the axis of the filter and the passageway is capable of putting all the inlets of the filtering elements successively in communication with an impurities discharging chamber in which prevails a pressure lower than the pressure of the filtered liquid. The arm is connected to rotate with the driven member of a unidirectional step-by-step drive mechanism. The arm is also connected to rotate with the driven member of a second unidirectional step-by-step drive mechanism in the same direction as with the first drive mechanism.