A degassing valve in a flexible container is disclosed. The valve includes a generally flat valve seat on a truncated generally dome shaped structure, and the valve seat is raised a height above the valve chamber base surface. A resilient, non-perforated, non-spring-biased diaphragm is inter-engaged upon the valve seat and overlaps the valve seat outer periphery. The valve seat engages a central area of the diaphragm that is not proximate the perimeter of the diaphragm, and the dome shaped structure has a sectional radius greater than the diaphragm radius. A well is recessed into the valve seat in a direction away from the diaphragm by a depth less than the height of the valve seat above the valve chamber base surface.