Abstract: Apparatus is provided for installation in the water tank of a toilet to reduce the quantity of water discharged from the tank during flushing while maintaining a satisfactory flushing action. The apparatus comprises a pair of flat, flexible partition elements which extend in a bowed manner between the front and rear walls of the tank on opposite sides of the tank-drain. A bead of deformable gasket material extends along the side and bottom edges of each partition, and the bead is urged into frictional engagement with the walls by the tendency of the partition to straighten from its bowed position. The partition elements form pockets on each side of the drain for containing water near the bottom of the tank while permitting water above the drain and the pockets to flow down the drain when the toilet is flushed.