A one-piece wash arm is provided for a dishwasher. The wash arm has an open channel through which water from a water supply hose is directed. The channel has opposite curved ends with discharge openings through which the water is sprayed onto objects to be washed in the dishwasher. The flow of water through the channel and the curved ends imparts rotation to the wash arm. In a preferred embodiment, the open channel is downwardly facing, and the water is substantially maintained in the channel due to the water pressure, velocity and surface tension. In an alternative embodiment, the open channel is directed upwardly.