In the inclined plate separator depicted below, the oily water mix enters from the left and flows through the plate bundle. The plates in the bundle are usually set at an angle around 45°. As oil builds up in the separator, it fills the upper passages in the bundle causing higher velocities through the lower plates. As the liquid exits the plates it is directed at the interface. Directing the water at the interface causes remixing of the oil, especially if there is a rag layer, with the exiting water. This remixing becomes more pronounced as the oil layer gets thicker. Dirty water will have fewer passages to go through, increasing its velocity and remixing ability.