Current International Plumbing Code (IPC), which both the JCSA and Virginia Department of Health adhere to, require a minimum of 2 compartments with flow between each compartment Grease Interceptor designed for FOG retention. Wastewater enters on the building side and exits the interceptor at the downstream outlet, minus the FOG component.

The capacity of the interceptor provides adequate time so that the wastewater has time to cool, allowing any remaining grease not collected by the traps time to solidify and accumulate until the interceptor is cleaned. With the size of this system, cleaning is usually extended to a weekly/monthly calendar, but must be done by a septic service contractor. If the facility anticipates excessive peak flows, a second grease interceptor is placed in series and immediately downstream of the first to catch any overflow.