A vacuum valve comprises inlet (10) and outlet (12) pipes connected together to form a pipe line through which sewage flows, a valve element (14) inclined to the pipe line and providing a selective communication between the inlet and outlet pipes (10,12), and a flexible or movable partition (18) mounted within the valve (14) to define a pressure chamber (20) and connected to the valve element (14). The valve element (14) is moved in an inclined manner in response to pressure differential between the pressure chamber (20) and the interior of the outlet pipe (12). The outlet pipe (12) has an axis displaced in a direction at right angles to the axis of the inlet pipe (10) and away from the valve element (14).