Abstract: A coupling connects a pressurized flush water vessel held in a toilet tank to a toilet bowl. The coupling has a passageway which provides direct fluid communication between the vessel and the bowl and a chamber for accumulating drainage, which may be exhausted into the toilet tank from inlet devices for the pressure vessel. A swinging door type one way valve substantially seals against leakage from the passageway to the chamber but allows drainage accumulated in the chamber to flow through a port to the passageway. The inlet to the chamber is above the port and at or below the bottom of the toilet tank and the port and the chamber inlet open above the spill level of the toilet. The inlet of the coupling is offset from the outlet and a cradle elevates the pressure vessel above the toilet tank bottom and captures heads of fasteners which secure the toilet tank to the toilet bowl.