Abstract: A "dump" valve for a concrete pumping line includes a tubular valve body for in-line connection in a distribution line and an end hinged cover plate for opening the valve. The valve includes a short rectangular discharge pipe, including flat walls, secured in a rectangular side wall opening in the valve body. The pipe has an outer flat end. A valve cover plate somewhat larger than the rectangular discharge pipe is provided with a sealing, gasketed face. The cover plate is hinged at one axial end to the valve body and is pivotally mounted to move between a closed position engaging the flat end of the discharge pipe and a pivoted depending open position in which the plate is swung clear of the bottom end of the discharge pipe section. An operating handle having an over-the-center latch linkage is coupled to the cover.