A pressure-assisted flush water tank includes a fluid container, a Venturi nozzle, a baffle and a buoy. The fluid container has an accommodating chamber, a water channel and an air channel. The accommodating chamber has a fluid inlet. The water channel and the air channel are in communication with the fluid inlet. The Venturi nozzle is disposed at a junction of the water channel and the fluid inlet. The baffle is configured to seal the air inlet in a movable manner. The buoy is disposed on an inner side of the air inlet. The top end of the buoy leans against the baffle. The buoy rises under internal pressure of the fluid container until the air inlet is closed. Before the buoy closes the air inlet, the protruding post abuts against and lifts up the baffle to open the air inlet.

A pressure-assisted flush water tank includes a fluid container, a Venturi nozzle, a baffle and a buoy. The fluid container has an accommodating chamber, a water channel and an air channel. The accommodating chamber has a fluid inlet. The water channel and the air channel are in communication with the fluid inlet. The Venturi nozzle is disposed at a junction of the water channel and the fluid inlet. The baffle is configured to seal the air inlet in a movable manner. The buoy is disposed on an inner side of the air inlet. The top end of the buoy leans against the baffle. The buoy rises under internal pressure of the fluid container until the air inlet is closed. Before the buoy closes the air inlet, the protruding post abuts against and lifts up the baffle to open the air inlet.

A tank for a pressure-assist toilet flush system includes a base and a cover formed of a composite material including a polymer matrix of a crystalline polymer material, with a short fiber reinforcement material having a fiber length of 0.125 inch to 0.177 inch dispersed therein at a fill ratio of 25-35%. The base has a bottom wall and a plurality of base sidewalls extending upward from the bottom wall to an upper end of the base, with an outlet defined in the bottom wall. The cover has an inlet for receiving water into the tank and includes a top wall and a plurality of cover sidewalls extending downward from the top wall to a lower end of the cover. The inlet is defined in the top wall, and the lower end of the cover is connected to the upper end of the base.