Patent ID: 8714917

Claim:
A pump comprising: a) a volute comprised of a volute front wall, a volute side wall, and a volute back wall enclosing a volute cavity; b) an impeller comprising a disc-shaped flange having a front side, a back side proximate to the volute back wall, and a plurality of back vanes on the back side of the flange, wherein the back vanes have a length extending from a central region of the impeller toward an outer region of the impeller, and wherein the disc shaped flange forms a fluid-impermeable barrier between a rear portion of the volute cavity between the back vanes and the back volute wall and a front portion of the volute cavity between the front side of the flange and the front wall of the volute; and c) a bleed hole formed in the volute back wall in communication with the portion of the volute between the back vanes and the volute wall, and the exterior of the volute; wherein the bleed hole is located midway along the length of the back vanes.