A device for use within a backhead of a down-the-hole percussive drill, for removing debris from a drillhole, includes a separator for separating water and other matter from the percussive fluid prior to the percussive fluid actuating the piston of the drill. The water and other matter are exhausted out the drill bit, to remove the debris. The device includes a one-way flow valve to prevent backflow of debris and water into the drillhead during periods when the percussive fluid flow ceases. The device can be added to existing drill backheads, or included as part of newly manufactured units.