Abstract: A deaerator tray in the form of a horizontally elongated trough for receiving a quantity of liquid to be deaerated. The trough has a flat bottom having a pair of spaced, elongated sides having upper liquid overflow edges. Guide structure is provided for directing the flow of liquid overflowing from the edges, the guide structure includes a pair of flat elongated inclined wall members each directly connected to a respective one of the sides below the upper liquid overflow edges along the length thereof. The wall members extend outwardly away from each other and downwardly away from the respective upper liquid overflow edges. Each wall member is inclined relative to the vertical and terminates in a lower edge to enhance deaeration of the liquid as the latter is guided down the wall members and falls from the lower edge.