A valve having a conduit, a sprung gate seated in a pocket within the conduit to control fluid flow through the conduit, and an actuator connected to the sprung gate that moves the sprung gate between an open position and a closed position, the sprung gate comprising: a first endless elastic band having an inner perimeter defining an open space;and a first gate member and a second gate member each defining an opening therethrough in an open position portion thereof and defining a closed position portion that obstructs the conduit to prevent fluid flow through the conduit, and each having tracks in an interior surface and positioned inset a distance from an outer perimeter of the first gate member and second gate member; wherein the first endless elastic band is sandwiched between the first and second gate members (230, 232) with the open space thereof oriented for alignment with the opening in both of the first and second gate members (230, 232), which are aligned to form a passage through the sprung gate; wherein the pocket includes a vent port; wherein the conduit is separated into a first and a second section by the pocket; wherein the first endless elastic band is received in the tracks of the first and second gate members (230, 232), with a first side received in one track and a second side received in the other track, which insets the first endless elastic band a distance from an outer perimeter of each of the first and second gate members (230, 232) and the first endless elastic band spaces the first and second gate members (230, 232) apart a distance from one another to define a channel around the outer surface of the first endless elastic band between the first and second gate member (230, 232) for fluid flow around the sprung gate within the pocket for fluid communication with the vent port; wherein the first endless elastic band is compressed between the first and second gate members (230, 232) as the sprung gate is inserted into the pocket, wherein the first endless band, the first gate member, and the second gate member are collectively movable linearly between the open position and the closed position within the pocket of the conduit, and wherein the first endless elastic band functions as a spring acting parallel to the direction of flow through the conduit the valve being characterised in that the first endless elastic band biases the first and second gate members (230, 232) into a sealing engagement with opposing walls of the pocket. a first endless elastic band having an inner perimeter defining an open space;and a first gate member and a second gate member each defining an opening therethrough in an open position portion thereof and defining a closed position portion that obstructs the conduit to prevent fluid flow through the conduit, and each having tracks in an interior surface and positioned inset a distance from an outer perimeter of the first gate member and second gate member; wherein the first endless elastic band is sandwiched between the first and second gate members (230, 232) with the open space thereof oriented for alignment with the opening in both of the first and second gate members (230, 232), which are aligned to form a passage through the sprung gate; wherein the pocket includes a vent port; wherein the conduit is separated into a first and a second section by the pocket; wherein the first endless elastic band is received in the tracks of the first and second gate members (230, 232), with a first side received in one track and a second side received in the other track, which insets the first endless elastic band a distance from an outer perimeter of each of the first and second gate members (230, 232) and the first endless elastic band spaces the first and second gate members (230, 232) apart a distance from one another to define a channel around the outer surface of the first endless elastic band between the first and second gate member (230, 232) for fluid flow around the sprung gate within the pocket for fluid communication with the vent port; wherein the first endless elastic band is compressed between the first and second gate members (230, 232) as the sprung gate is inserted into the pocket, wherein the first endless band, the first gate member, and the second gate member are collectively movable linearly between the open position and the closed position within the pocket of the conduit, and wherein the first endless elastic band functions as a spring acting parallel to the direction of flow through the conduit the valve being characterised in that the first endless elastic band biases the first and second gate members (230, 232) into a sealing engagement with opposing walls of the pocket.