Grease Interceptors

What is a Gravity Grease Interceptor?


An in ground gravity grease interceptors (GGI’s) is an in-ground vault, roughly the size of a septic tank, with a minimum capacity of 700 gallons, but normally consisting of 1,000 gallons or more. It is located and installed in the ground on the exterior, private side, of the building or property. Wastewater enters on the building side and exits the interceptor at the downstream outlet, minus the FOG component.

Diagram showing a grease interceptor flow system
gravity grease interceptor

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.

Note: This page is provided for informational purposes for owners and managers of existing in ground gravity grease interceptors (GGI’s), as GGI’s are typically no longer allowed for new installations. For more information see the Hampton Roads Regional Technical Standards for Grease Control Devices.