A flushing mechanism for flushing a toilet bowl with a reduced amount of water. The flushing mechanism includes a containment vessel adapted to fit in a standard-sized toilet tank and means within the containmment vessel for forcing water out of the vessel into the bowl to be flushed. In a first embodiment, the containment vessel includes an elastic bladder which is filled with the liquid and expands to provide the additional pressure. In a second embodiment, a piston spring system forces liquid out of the containment vessel to flush the bowl. A hydraulic actuation system is also provided for actuating the flushing mechanisms.