A valve for controlling the level of liquid within a chamber (10) is disclosed.The valve comprises a liquid inlet (30) and a primary float (40) that is movablein response to a change in the level of liquid (20) within the chamber (10) betweenan open configuration in which liquid (20) is able to flow through the liquid inlet(30) into the chamber (10) when the liquid (20) within the chamber (10) is belowa predetermined acceptable level, and a closed configuration in which liquid(20) is prevented from flowing through the liquid inlet (30) into the chamber(10) when the liquid within the chamber (10) is at or above the predetermined acceptablelevel. The valve also includes a secondary float (50) that is movable in responseto an increase in the level of liquid within the chamber (10) above the predeterminedacceptable level from an inoperative configuration to an operative configurationin which the secondary float (50) imparts a force upon the primary float (40) thaturges the primary float (40) towards its closed configuration.
