wall 72 in the bottom of the housing 12 of the handpiece arcuate guides 74 extend upward at an angle from the opening 70 and house a button 76 which has a cross bar 78 disposed across its inner end a spring 80 urges the button outward so that the cross bar 78 pinches the tube 68 against a stationary stop 82 to close off the water supply therethrough thus flow of water through the tube 68 and out the nozzle 56 may be controlled by pressing or releasing the button 76 the drive unit 14 is disclosed in fig4 it comprises a shallow cup 84 having a central recess 86 fig5 which receives the hub 88 of an impeller 90 preferably as shown the impeller is of the bucket type having buckets 90a and it is shaped more or less like a bicycle sprocket but having substantial width with the cover 92 bolted in place on the cup 84 the upper end of the hub 88 fits into the recess 94 in its center the impeller is formed with a coupling 96 similar to coupling 42 in the handpiece and presenting a square opening 98 receiving the square driving end 100 of the wire 52 of the flexible drive 20 a second swivelling b n c coupling 102 secures the end of the nylon casing 48 of the flexible drive to the molded female tubular end 104 of the cover 92.