<p>A valve assembly for use in for example a stirrup pump. The valve assembly has a body defining a bore into which a carrier is inserted. The carrier defines a tubular passageway with a pair of O-rings spaced apart along the length of that passageway. The passageway is of substantially uniform internal diameter and the O-rings are received in annular grooves formed in the inside surface of the passageway. Two balls are provided each associated with one of the O-rings and an inlet port is provided which communicates with the space in the passageway between the O-rings. The application of an excess pressure to the port drives fluid from the port through one of the O-rings whereas the application of a reduced pressure to the port draws fluid through the other O-ring to the port.</p>
