Abstract: Disclosed herein is a dishwasher having a rack which has a circular protusion formed around its outer periphery so that the rack can be removably suspended from the upper inner periphery of the diswasher tub. A rotary nozzle head assembly is rotatably secured to a central portion of the bottom of the dishwasher tub and connected at its lower end to a water pressure supply. The rotary nozzle head includes a plurality of nozzles for spraying the contents of the dishwasher tub retained in the rack. One of the nozzles in the nozzle head is located to spray against one of the impeller vanes formed on a rotary impact impeller provided at the top of the rotary nozzle head assembly. This causes another impeller vane to impact against an annular supporting frame secured to the top of the rotary nozzle head. In this way, the rotary nozzle head rotates intermittently for effective washing of the contents of the dishwasher tub.