Toilet tank flush valve for partial or full flush

In combination with a flush tank having a downwardly open outlet and means for filling the tank with a liquid, a flush valve comprising:

• 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, the float having a low buoyancy insufficient to hold the tube upper end above the liquid level when the compartment is 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;
• a vertically displaceable actuating rod extending along an upright axis and having an externally accessible upper end and an actuating formation engageable vertically downward against the float to submerge the float and fill the compartment, whereby when the compartment is filled the float is changed from high buoyancy to low buoyancy and the tube upper end sinks below the liquid level and causes the liquid in the tank to flow through the tube out of the outlet;
• and
• stop means including stop formations on the tube and on the rod engageable for limiting downward displacement of the float and tube to an intermediate position above the lower position and disengageable to allow downward displacement of the float and tube into the lower position.