Abstract: An apparatus for use in converting solid thermoplastic material to molten thermoplastic material includes a tank which receives the solid thermoplastic material and holds a body of molten thermoplastic material. A housing encloses the tank. The tank and housing have openings through which solid thermoplastic material enters the tank. A rim extends along the periphery of an upper wall of the housing. The rim has an upper edge portion which is disposed above the upper wall of the housing to enable the rim to block wash water and/or other liquids from flowing along the upper wall of the housing into the tank. A cover assembly is connected with the housing and is movable between an open condition and a closed condition blocking the open upper end portion of the tank. The cover assembly includes an inner cover which sealingly engages the upper edge portion of the rim and an outer cover which cooperates with the housing to enclose the inner cover.