Compact ball joint assembly for piping system has ball and socket portions which may be formed of pipe. A reaction member held internally of the socket portion by retaining means such as a retaining ring or radially extending socket screws provides a support for a plurality of adjustment screws which can be moved in a direction parallel to the axis of the socket portion for forcing a pressure ring positioned for axial movement within the socket against a sealing ring which bears against the ball portion of the joint.