The Heli-Sep is the most effective, efficient oily water separator available. A unique concept utilizing the dual capabilities of gravity assist separation and coalescence provides a permanent separating media which is non-fouling. This feature provides the distinct advantage of eliminating the ongoing expense associated with the continual replacement of expendable media and filters. This exclusive design incorporates a matrix plate pack consisting of corrugated plates assembled in a crisscross pattern. This configuration allows increased contact time of the oily water with the plate pack thus enhancing the coalescing of the oil. The matrix plate pack is followed by a polishing pack that scrubs the remaining oil out of the water.