Abstract: An apparatus for spray washing the interior of vessels includes a body member secured to a fluid supply line, and a housing rotatably secured to the body and in flow communication therewith. A hub is rotatably secured to the housing on an axis transverse to the body-housing axis, and a plurality of nozzles extend radially from the hub perpendicular to the hub axis. A pair of reaction jets also extend radially from the hub to drive the hub in an oscillating motion. The hub is secured to a spindle which is joined to a lever which operates an over center toggle. The toggle operates a valve which alternates the fluid flow to the reaction jets to produce the oscillating hub motion. The lever also drives a ratchet mechanism which incrementally rotates the housing about the body member.