In combination, a slurry pump side part and a slurry pump impeller, - the impeller comprising a front shroud (500, a back shroud and a plurality of pumping vanes therebetween, the front shroud having an outer face and an impeller inlet extending through the front shroud, the impeller inlet being coaxial with an impeller rotation axis (X-X), the front shroud outer face including an outer region, an inner region and an intermediate region therebetween, the intermediate region being in a plane generally at right angles to the impeller rotation axis (X-X) and the inner region being inclined towards the pumping vanes; - the pump side part comprising a side wall section having a front face and a rear face, the pump side part further comprising an inlet section extending from the front face and arranged when in use to be coaxial with the impeller rotation axis (X-X), the rear face including an outer region with an outer edge in a plane which is substantially at right angles to the rotation axis (X-X), an inner region with an inner edge and an intermediate region between the outer and inner regions (60, 62) which is inclined from the said plane in a direction towards the inlet section, the inner region extending in a direction away from the intermediate region and in a direction away from the front face of the side wall section and generally following the inner region of the outer face of the impeller front shroud, wherein the outer face of the impeller front shroud (500 and the rear face of the pump side part are arranged in use to be facing one another with a gap therebetween the gap having an outer opening and an inner opening, the rear face of the side wall section being configured so that the cross-sectional dimension of the gap increases in a direction toward the impeller rotation axis (X-X) in the intermediate region, and the inner region terminating at the inner opening. - the impeller comprising a front shroud (500, a back shroud and a plurality of pumping vanes therebetween, the front shroud having an outer face and an impeller inlet extending through the front shroud, the impeller inlet being coaxial with an impeller rotation axis (X-X), the front shroud outer face including an outer region, an inner region and an intermediate region therebetween, the intermediate region being in a plane generally at right angles to the impeller rotation axis (X-X) and the inner region being inclined towards the pumping vanes; - the pump side part comprising a side wall section having a front face and a rear face, the pump side part further comprising an inlet section extending from the front face and arranged when in use to be coaxial with the impeller rotation axis (X-X), the rear face including an outer region with an outer edge in a plane which is substantially at right angles to the rotation axis (X-X), an inner region with an inner edge and an intermediate region between the outer and inner regions (60, 62) which is inclined from the said plane in a direction towards the inlet section, the inner region extending in a direction away from the intermediate region and in a direction away from the front face of the side wall section and generally following the inner region of the outer face of the impeller front shroud,