A rotary coupler having two housing portions, one housing portion being rotatable with respect to the other housing portion includes two fluid channels including a water channel extending axially the length of the coupler and a slurry channel disposed radially outwardly of the water channel. A flow directing surface is disposed within the rotatable housing portion to direct a slurry of abrasive particles and air through the housing to the outlet in a continuous manner substantially without disruption of the compositional integrity of the slurry.
