Abstract: A pump assembly (1) includes a pump (2) and an electric motor (30 comprising a stator (4) and a rotor (5) separated by a gap. The pump assembly has a casing (6) defining a housing accommodating the stator (4) and rotor (5) with a removable seal jacket (12) that is designed to move from a test configuration where the seal jacket (12) is removably mounted within the casing (6), in the gap, to a normal operating configuration, where the seal jacket (12) is removed from the casing (6) to form a wet stator arrangement. Methods of manufacturing and installing the pump assembly are also disclosed.