We make our Gravity Flow Oil / Water Separator Tanks from Fiberglass, a durable and non corrosive material that will not be affected by most chemicals.

A Water/ Oil separator Tank is made with an internal baffle, creating two chambers. Retaining the incoming oil and grease bearing liquid in the first chamber. allowing the oil and grease to rise to the top of the tank, where it will be removed with intervals.
The clean water will then flow through an opening at the bottom of the baffle into the second chamber and discharged.
The tanks can be made in volumes to suit your project.