A pump housing assembly which includes a pump casing and a liner, where the pump casing includes at least two parts which are adapted to be connected together in an assembled position with the pump casing having opposed front and rear sides and a common junction region which is disposed within one or more planes which pass through the front and rear sides of the assembled pump casing, the liner being formed in one piece and having sealing portions that are activated to provide a seal between the liner and the pump casing.