Abstract: A washing machine including a boiler, a motor-driven pump controlled by a control device to pump warm water from the boiler to a spray gun through a water supply pipe, a check valve installed in the water supply pipe, a water return pipe for sending water from the water supply pipe back to the boiler, an unload valve for releasing pressure from the water supply pipe, a water volume detector connected to the water supply pipe between the unload valve and the spray gun to accumulate water from the water supply piping and being actuated when accumulated water volume drops below a predetermined value, a pressure detector mounted on the unload valve and actuated when the unload valve is opened, and a control device driven by the water volume detector to start the motor when the water volume detector is actuated, or driven by the pressure detector to turn off the motor when the pressure detector is actuated.