A rotary tank cleaning spray nozzle assembly comprising: a stationary outer housing; a liquid inlet disposed at an upper end of said stationary housing for connection to a liquid supply and for direction of liquid into said stationary housing; a rotary housing disposed below said stationary housing for rotation relative to said stationary housing about a central axis of said stationary housing; a nozzle hub having at least one liquid spray nozzle, said nozzle hub being mounted on said rotary housing for rotation relative to said rotary housing about an axis transverse to the central axis of said stationary housing; a fluid driven drive mechanism including a stator mounted within said stationary housing for tangentially directing liquid passing through said stationary housing, a rotor associated with said rotary housing for rotation as an incident to the tangential direction of liquid from said stator for rotating said rotary housing relative to said stationary housing; said rotary housing and nozzle hub having cooperating gears (90a, 91a) for rotating said nozzle hub relative to said rotary housing as an incident to rotation of said rotary housing with respect to said stationary housing; and characterized by a support rod having a bottom support for supporting said rotary housing for relative rotation and extending upwardly through the rotary housing into the stationary housing and through said rotor and stator, and a releasable support rod retainer engageable with an upper end of said support rod for supporting the support rod against rotation and with the support rod retaining the rotary housing in operative relation to the stationary housing for relative rotation. a stationary outer housing; a liquid inlet disposed at an upper end of said stationary housing for connection to a liquid supply and for direction of liquid into said stationary housing; a rotary housing disposed below said stationary housing for rotation relative to said stationary housing about a central axis of said stationary housing; a nozzle hub having at least one liquid spray nozzle, said nozzle hub being mounted on said rotary housing for rotation relative to said rotary housing about an axis transverse to the central axis of said stationary housing; a fluid driven drive mechanism including a stator mounted within said stationary housing for tangentially directing liquid passing through said stationary housing, a rotor associated with said rotary housing for rotation as an incident to the tangential direction of liquid from said stator for rotating said rotary housing relative to said stationary housing; said rotary housing and nozzle hub having cooperating gears (90a, 91a) for rotating said nozzle hub relative to said rotary housing as an incident to rotation of said rotary housing with respect to said stationary housing; and characterized by a support rod having a bottom support for supporting said rotary housing for relative rotation and extending upwardly through the rotary housing into the stationary housing and through said rotor and stator, and a releasable support rod retainer engageable with an upper end of said support rod for supporting the support rod against rotation and with the support rod retaining the rotary housing in operative relation to the stationary housing for relative rotation.