Abstract: A waste water reuse system comprised of a first holding tank for disposition above the toilet tank of a conventional toilet, the holding tank having a waste water inlet located adjacent a top thereof, an overflow outlet located below the waste water inlet, a removable filter disposed within the holding tank between the inlet and outlet in a position to filter water incoming from the inlet, a gravity fed outlet at the bottom of the tank for connection to a water inlet of the conventional toilet, a water supply inlet at or adjacent the bottom of the tank for connection to a fresh water supply, and a float valve connected to the water supply inlet for controlling inflow of fresh water to the holding tank, the float valve having a float ball for causing shut-off of the supply of fresh water at a level substantially below the overflow outlet, and apparatus connecting the waste water inlet to a bathtub water outlet.