Abstract: A hopper vessel has a series of discharge valve members in the bottom, which valve members can swing about a transverse axis from a horizontal postion, in which they close the bottom openings of the hold of the vessel, into a vertical position, in which they fully open said bottom openings, which valve members also can be placed in an inclined intermediate position in which they still close the bottom openings, said valve members being provided with channels which are in line with channels in the intermediate parts of the bottom and with a conduit connected to a pump, and the bottom openings, at the level of the valve members, having openings in the side walls connecting to water supply which openings are closed in the horizontal position of the valve members by said valve members and opened in the intermediate position whereby water entering through the openings assists in the discharge of material through the conduit with at least one valve member in said intermediate position.