Abstract: A toilet seat includes a substantially rigid lid coupled to a pliant top. The seat seals against the rim of the standard toilet bowl and forms a pressure-adjustable cavity with the bowl and the surface of the water. Once sealed, the seat is pumped to inject air into the cavity, thereby increasing the pressure in the cavity to cause a flush operation. The lid and top each have one way pressure valves permitting air to flow into the cavity as the top is pumped. In another embodiment, the toilet has a standard toilet seat and is connected to a vacuum source via a selectively operable valve. The valve is selectively operable between an open state and a closed state, the open state creating a fluid communication path between the vacuum source and the void volume, the closed state providing a substantially airtight seal between the void volume and the vacuum source.