Abstract: A washing machine including a tub having a helical flow path defined by a channel and a sump located at a lower end of the channel with a dam therein is described. In an exemplary embodiment, a water outlet is located in the sump, and the dam is positioned in the sump upstream from the outlet. The dam, in the exemplary embodiment, is substantially perpendicular to flow path and extends from a tub sidewall to at least beyond the outer perimeter of the water outlet. The dam has a sufficient height to prevent debris heavier than water from flowing from the channel to the outlet during a non-spin portion of a wash cycle, yet is low enough so that when the spin cycle is initiated, the debris will flow over the dam to the outlet.