the shaft 40 referring still to fig3 and 4 on the front surface of the backer plate 44 the single vane 50 extends both axially toward the pump inlet 24 and also from a periphery of the backer plate 44 toward but not to its center over most of this latter extension the vane 50 extends axially to a uniform height above the backer plate 44 however at its portion closest to the center of the backer plate 44 the vane 50 tapers downward toward the front surface of the backer plate 44 as shown best in fig4 referring now to fig5 the vane 50 is curved to present a convex surface as it advances with operation of the motor as indicated by direction arrow 53 the outlet 26 is directed tangentially to this rotation of the impeller assembly 46 to receive water accelerated by the vane 50 the single vane 50 is positioned substantially on one half of the front surface of the backer plate 44 so that its axial ridge 51 subtends from the center 60 of the backer plate 44 an angle u03b1 less than 180 u00b0 and the entire vane 50 is contained within a subtended angle of less than 270 u00b0 the edge of the vane 50 closest to the center 60 of the backer plate 44 is displaced from the center 60 of the backer plate 44 while.