Gas distribution assemblies and methods for providing a flow of gases to a process station are described. The gas distribution assemblies comprise a pumping liner with a showerhead and a gas funnel positioned therein. The pumping liner has an inner wall that slants at a first angle relative to a central axis of the gas distribution assembly so that the inner wall adjacent the bottom wall of the pumping liner is closer to the central axis than the inner wall adjacent the top wall. The gas funnel and pumping liner form a plenum between the outer wall of the gas funnel, a cavity in the bottom wall of the gas funnel and the inner wall of the pumping liner.