Home › Two Devices, One Word, Different Jobs

Two Devices, One Word, Different Jobs

The terms get used as though they were interchangeable. They are not, and which one a kitchen has changes the service, the schedule and the cost.

The short form

A grease trap is the smaller indoor device rated by flow, roughly 5 to 100 gallons per minute. An interceptor is the in-ground vessel, typically 2,000 gallons or more, rated by volume. Both work the same way: grease cools, floats, and is held above an outlet that draws from beneath it.

Source: U.S. EPA, FOG Management and Control Program.

InterceptorCall is a referral service, not a contractor. We connect operators and property managers with independent contractors. Contractors and waste haulers are required to hold whatever credential and permit their state or municipality demands — ask to see them, because the manifest they leave you is a compliance record. We carry out no work, we haul nothing, we do not set prices, and we never charge the caller anything. Nothing here states the grease limit, the pumping interval or the device size that applies to any particular kitchen; those are set by your control authority and by your installation.

What both of them do

Both work on the same principle, and it is worth seeing once because every other rule on this site follows from it.

Grease floats, solids sink, and the outlet reaches into the band between them. Both layers grow, the band shrinks, and everything else about these devices follows from that.

Grease floats. Solids sink. The outlet reaches into the band between them, and a baffle forces flow to take the long way around so there is time for the separation to happen.

The trap: small, indoors, rated by flow

A grease trap is the smaller device — under a sink, set into a floor, or hung outside a wall. EPA’s material describes them in a range running from about 5 gallons per minute and 10 pounds of grease capacity up to around 100 gallons per minute and 200 pounds.

They are rated by flow, they need a flow restrictor in front of them, and because they are small they fill quickly and are serviced often.

Source: U.S. EPA, FOG Management and Control Program.

The interceptor: large, outdoors, rated by volume

An interceptor is the in-ground vessel, typically 2,000 gallons or more, in concrete, fiberglass, plastic or steel. Its advantage is retention time: more volume means more minutes for grease to rise before the water reaches the outlet.

EPA’s material notes a preference for monolithic, single-piece construction over two-piece designs, because a seam is a place that leaks.

Why it decides the service

A trap is a frequent, small, indoor job that can often be done between services. An interceptor is a vacuum truck in the parking lot, a manifest, and a schedule that has to be arranged. They are different trades and, in most kitchens, different visits.

So the first question any contractor should ask you is which you have, where it is, and how big. If nobody asks, that is informative.

And when both are present

Plenty of kitchens have small traps on particular fixtures and an interceptor outside taking the rest. EPA’s material treats series installation — one device feeding the next — as the preferred arrangement over parallel, which has more that can go wrong.

Knowing your own arrangement before you call is worth more than any description of the problem. Sizing, and why bigger is not automatically better.

Have the last manifest in front of you.Date, hauler, volume removed and where it went — it is the first thing anyone asks for and it tells a contractor more about the state of the vessel than a description does. We will route you to somebody who covers your area, identified from the ZIP code of the premises, and you are never charged. Other plumbing work at the premises can be arranged through the same call.

Call (888) 753-1770