A pump (10) includes an impeller (12) positioned in a housing (11). A valve assembly (13) is positioned within a valve sleeve (25) which is carried by the impeller (12). The impeller (12) is carried by an armature (27), and a pocket (28) is formed between the impeller (12) and the armature (27) adjacent to the valve sleeve (25). One or more elastomeric members (29) are positioned in the pocket (28) to surround the impeller (12) at the area of the valve sleeve (25) to provide a retaining force on the valve sleeve (25).