A valve for use in a compounding device, said compounding device including at least one pump for causing fluid to move from at least one source container to at least one receiving container, comprising: a valve housing; a valve structure (21a, 21b) is located within the valve housing, includes an input aperture (21a1, 21b1) located at a top of the valve structure (21a, 21b) and an exit aperture (21a3, 21b3) defined in a peripheral side wall of the valve structure (21a, 21b), and is configured to permit fluid to flow through the valve (21a, 21b) when in an open position, characterized in that the valve structure (21a, 21b) is rotatably driven about a rotational axis and with respect to the valve housing by an actuator (102a, 102b) for selectively fluid-connecting the at least one source container with the at least one receiving container depending on a rotational position of the valve structure (21a, 21b) and includes a gravity wall (21a2, 21b2) initially extending obliquely from an inner peripheral wall of the valve structure (21a, 21b) and extending downward and substantially parallel with the rotational axis of the valve structure (21a, 21b) wherein, when the valve structure (21a, 21b) is in the open position, fluid moving through the valve structure (21a, 21b) due to operation of the pump moves upward against a force of gravity when travelling through the valve and traversing between the gravity wall (21a2, 21b2) and the valve housing which form a trap structure, and wherein the input aperture (21al, 21bl) is configured such that fluid entering the valve structure (21a, 21b) through the input aperture flows along a downward fluid path and substantially parallel with the rotational axis of the valve structure (21a, 21b); the exit aperture (21a3, 21b3) is configured such that fluid exiting the valve structure (21a, 21b) through the exit aperture flows along an exit path that is substantially perpendicular to the rotational axis of the valve structure (21a, 21b); and the gravity wall (21a2, 21b2) located within the valve structure (21a, 21b) and configured such that fluid travelling through the valve travels along the downward fluid path at an upstream side of the gravity wall (21a2, 21b2), and travels on an upward fluid path on a downstream side of the gravity wall (21a2, 21b2), wherein the upstream side and downstream side of the gravity wall (21a2, 21b2) are opposed to each other, and a direction of the downward fluid path is generally opposed to a direction of the upward fluid path. a valve housing; a valve structure (21a, 21b) is located within the valve housing, includes an input aperture (21a1, 21b1) located at a top of the valve structure (21a, 21b) and an exit aperture (21a3, 21b3) defined in a peripheral side wall of the valve structure (21a, 21b), and is configured to permit fluid to flow through the valve (21a, 21b) when in an open position, characterized in that the valve structure (21a, 21b) is rotatably driven about a rotational axis and with respect to the valve housing by an actuator (102a, 102b) for selectively fluid-connecting the at least one source container with the at least one receiving container depending on a rotational position of the valve structure (21a, 21b) and includes a gravity wall (21a2, 21b2) initially extending obliquely from an inner peripheral wall of the valve structure (21a, 21b) and extending downward and substantially parallel with the rotational axis of the valve structure (21a, 21b) wherein, when the valve structure (21a, 21b) is in the open position, fluid moving through the valve structure (21a, 21b) due to operation of the pump moves upward against a force of gravity when travelling through the valve and traversing between the gravity wall (21a2, 21b2) and the valve housing which form a trap structure, and wherein the input aperture (21al, 21bl) is configured such that fluid entering the valve structure (21a, 21b) through the input aperture flows along a downward fluid path and substantially parallel with the rotational axis of the valve structure (21a, 21b); the exit aperture (21a3, 21b3) is configured such that fluid exiting the valve structure (21a, 21b) through the exit aperture flows along an exit path that is substantially perpendicular to the rotational axis of the valve structure (21a, 21b); and the gravity wall (21a2, 21b2) located within the valve structure (21a, 21b) and configured such that fluid travelling through the valve travels along the downward fluid path at an upstream side of the gravity wall (21a2, 21b2), and travels on an upward fluid path on a downstream side of the gravity wall (21a2, 21b2), wherein the upstream side and downstream side of the gravity wall (21a2, 21b2) are opposed to each other, and a direction of the downward fluid path is generally opposed to a direction of the upward fluid path.