Oily water enters the separator through a gravity fed inlet pipe. 1. The flow is directed downward and over a deflector baffle to dissipate the flow across the width of the separator. In the pre-separation chamber. 2. Heavy solids settle out and "slugs" of oil rise immediately and remain on the surface. The remaining oily water enters the MPak® coalescing plate packs 3. in the separation chamber. Buoyancy forces cause the oil droplets to rise and coalesce on the underside of the plates, slide up to the surface, and finally rise to the surface in the form of large globules. The effluent enters the clean water chamber 4. where it is discharged from the lower regions of the separator. The separated oil accumulates in the upper regions of the separator. An optional oil level sensor 5. will sound an alarm at high oil levels. Waste oil is drawn from the surface of the separator.