A fluid transfer system for an oil drilling rig which generally includes a portable housing container which includes a pump, a manifold, an air compressor and a pressure washer. The manifold will generally include three inlets, with a first inlet connected to a drilling rig, a second inlet connected to a first storage tank such as a water tank, and the third inlet connected to a second storage tank such as an invert tank. The pump is connected to the manifold to transfer mixed fluids back out the drilling rig. The air compressor is linked to the manifold flow blowing out the fluid conduits prior to transfer of the container or to prevent spillage. The pressure washer may be used to clean various components at the drilling site. The present invention is fully portable such that it may easily be packed up and transferred between multiple drilling sites for use.