A commercial ice maker purges water from a sump via a passive drain valve instead of an active drain pump. The ice maker uses a large freeze plate, but still can accommodate the passive drain valve within a standard enclosure footprint. A bottom wall of the ice maker has a drain passaging groove formed in an upper surface. The drain valve is supported above the bottom wall and drain tube is at least partially received in the drain passaging groove. The drain valve can include a valve body that has a valve seat and a movable valve member that opens and closes a valve passage through the valve seat. The valve member radially overlaps the valve seat along a longitudinal axis when the valve member is closed.