Abstract: A pressure flush system for use within a toilet tank includes a pressure flush tank which has an air inlet and a water inlet. Water is maintained with the pressure flush tank under air pressure. There is a water discharge for said tank to direct water to a toilet bowl. The tank contains a flushing valve system, which, when operated, will direct water under air pressure through said water discharge opening. The water discharge includes a housing which is attached to the bottom of the pressure flush tank and there is a one way check valve in the water discharge housing and located outside of the pressure flush tank. The one way check valve prevents water passing therethrough when the pressure flush tank is discharged and it permits the draining of water outside of the pressure flush tank and within the toilet tank through the water discharge opening.