PRESSURE WASHER WITH PRESSURE BYPASS

A pressure washer for delivering a liquid under high pressure has an inlet conduit connected to a liquid supply and an outlet conduit connected to a spray nozzle which can be operated to control the delivery of liquid through the nozzle. A bypass conduit enables recirculation of the liquid from the outlet conduit to the inlet conduit. A bypass system, disposed between the outlet conduit and the bypass conduit, includes a shuttle valve which moves between first and second positions at which it respectively blocks or opens the liquid path from the outlet conduit to the bypass conduit. The shuttle includes an axial passage from its inlet to its outlet side which passage has a narrowed jet outlet such that, when the liquid flows through the spray nozzle and the outlet conduit, the pressure drop across the shuttle moves the shuttle to the first position, while when the flow out the spray nozzle is stopped or significantly blocked, pressure on the side of the shuttle facing the spray nozzle rises to the level at the inlet side of the shuttle, which moves the shuttle to unblock the bypass conduit. A spring aids the return motion of the shuttle to the second position.