Abstract: A regenerative turbine pump apparatus which includes a housing having an inlet and an outlet and an impeller mounted for rotation within the housing. The impeller has an outer diameter and a channel ring is disposed around the impeller. The channel ring has a first arcuate portion that has a first radius to provide a substantially uniform first clearance with respect to the outer diameter of the impeller and the first arcuate portion extends throughout a major part of the channel ring. The channel ring includes a second arcuate portion proximate to the inlet having a second clearance with respect to the outer diameter of the impeller that is greater than the first clearance.