Abstract: This invention relates to the art of pressure vessels and more particularly to a valve assembly for use in a pressure vessel of the type having a rigid container with a deformable bladder therein, dividing the container into two variable volume chambers, one adapted to receive gas under pressure and the other to receive liquid under pressure.The valve assembly which is screwed into a port in communication with the gas chamber includes a slidably mounted stem having a resilient valve member at one end normally urged to seat on the beveled inner end of an axial bore in the valve assembly in a first seating position of the valve member, and urged further into said beveled inner end when the bladder is charged with gas under pressure in a second seating position of the valve member. The inward movement of the valve member is limited by a stop carried by the stem. When the liquid chamber is charged, if the bladder should abut against the resilient valve member, no extrusion of the bladder would occur.