Abstract: A pump is formed by a housing (10) having an inlet (11) and an outlet (12) for a fluid. The housing (10) contains a rotator (13) provided with at least one surface recess (17a, 17b, 17c, 17d) that forms with an interior surface of the rotor a chamber (18a, 18b, 18c, 18d) that, on rotation of the rotor (13), conveys fluid from the inlet (11) to the outlet (12). A flexible seal (23) is provided on or as part of the housing (10) and is located between the inlet (11) to the outlet (12) to engage the rotor (13) to prevent fluid passing from the outlet (12) to the inlet (11). A second inlet (16) is provided leading to the outlet (12) for the supply to the outlet (12) of a second fluid and the second inlet (16) also supplies the second fluid to the back of the seal (23) to urge the seal (23) against the rotor (13).