A system for fluid jet heads such as ink jet adapted for self-cleaning of certain clogs and purging of air from the head. The head includes a manifold communicating with at least one orifice to project a stream of fluid therefrom. Two fluid supply paths at different sides of the manifold supply pressurized fluid thereto. One of the supply paths is located at the top of the manifold and is reversible. If air or an impurity causing a nozzle clog is encountered in the head, the top path may be reversed so the fluid enters from one path and exits at the top. This establishes a crossing flow at the orifice, tending to loosen and remove the clog and purging the impurity or air from the head and out the reversible path.