Abstract: A flush tank has a tube fitted to a downwardly open outlet and having an upper end vertically displaceable in the tank. A float fixed to the tube can switch between a low buoyancy insufficient to hold the tube upper end above the liquid level and a high buoyancy capable of holding the tube upper end above a liquid level in the tank. An actuating rod has an upper end and can engage vertically downward against the float to submerge same and changed it from high buoyancy to low buoyancy so the tube upper end sinks below the liquid level and the liquid in the tank flows through the tube out of the outlet. Stops on the tube and on the rod are engageable for limiting downward displacement of the float and tube to an intermediate position and are disengageable to allow downward displacement of the float and tube.

Abstract: A flush tank has a downwardly open outlet, a valve for filling the tank with a liquid, and a flush valve having a tube fitted to the outlet and having an upper end vertically displaceable in the tank between an upper position and a lower position. A float fixed to the tube upper end and having an upwardly open compartment has a low buoyancy insufficient to hold the tube upper end above the liquid level when the compartment at least partially filled with water and a high buoyancy capable of holding the tube upper end above a liquid level in the tank when the compartment is empty.

Abstract: A flush tank having a downwardly open outlet and a valve for filling the tank with a liquid has a flush valve having a tube fitted to the outlet and having an upper end vertically displaceable in the tank. A float fixed to the tube upper tube end has a buoyancy changeable between a high buoyancy capable of holding the tube upper end above a liquid level in the tank and a low buoyancy insufficient to hold the tube upper end above the liquid level. An actuator connected to the float can temporarily change the float from high buoyancy to low buoyancy and thereby sink the tube upper end below the liquid level and cause the is liquid in the tank to flow through the tube out of the outlet. The float has a lower part annularly surrounding the tube and an upper part formed as an upper space having a large upwardly open mouth level with the upper end of the tube and a small opening below its mouth opening into the tube.