Abstract: A pressure washing machine has a valve assembly with an inlet opening and an outlet opening for a pressurized fluid, and a fluid interception element which is movable under the thrust of the fluid itself between a first operating position in which the fluid moves towards the outlet opening, and a second operating position in which the movement of the fluid is substantially inhibited; the valve assembly also has a by-pass valve, a shutter element of which is interposed between an inlet passage and an outlet passage of the valve itself and is controlled by a control element operated directly by the interception element to move the shutter element between a position in which the inlet and discharge passages are isolated from each other when the interception element is in its first operating position, and a position in which the passages are in communication with each other when the interception element is in its second operating position, irrespective of the pressure of the fluid in the outlet opening.