An improved valve assembly having an integral single piece housing (1) having an inlet (15), an outlet and defining an inwardly extending wall forming a valve seat (3); a valve member (4) moveable within the housing (1) between a closed position and an open position and a seal (11) to form a fluid tight seal between the valve member (4) and the valve seat (3) when the valve member is in the closed position. The seal (11) also acting to retain the valve member (4) within the housing (1) and in which the housing defining end portions which extend axially away from the valve member (4) at any position of the valve member between the open and closed positions.