Septic owner guide
Grease trap or interceptor? Which one this kitchen has, and who services it
Plenty of kitchen operators never learn what their drains run through. It might be a small box under the sink, a buried tank out by the dumpster, or both, and that answer decides whether the job belongs to the closing crew or to a pump truck.
Ask around a Pocatello kitchen what the grease trap is and you can get two honest answers that describe two different pieces of equipment. The dishwasher points under the sink. The owner points out the back door at a lid in the asphalt. Both call it the grease trap.
What is the difference between a grease trap and a grease interceptor?
A grease trap is a small unit that sits indoors at or under a fixture, usually the three-compartment sink, and catches grease from that drain. A grease interceptor is a large tank buried outside that the whole kitchen drains through before the sewer. The indoor box can be kept up in-house. The interceptor is emptied by a pump truck, which is what grease trap pumping in Pocatello means for most kitchens here.
| Indoor grease trap | Outdoor grease interceptor | |
|---|---|---|
| Where it sits | Under or beside a sink, or set into the floor near it | In the ground outside, lid flush with the lot or alley |
| What drains to it | One fixture, sometimes two | The kitchen’s whole grease-bearing line |
| Size | Small enough to open by hand | A buried tank, often on the scale of a home septic tank |
| How it gets emptied | Opened and cleaned out on a short cycle | Pumped down from a vacuum truck parked nearby |
The words get used loosely, and that is most of the confusion. Invoices and inspectors alike say “grease trap” for both, and someone searching for a grease interceptor near me is usually standing over the outdoor tank.
How do you tell which one a kitchen has?
Look in two places. Inside, check under and beside the three-compartment sink and the floor around it for a metal or plastic box with a bolted or clipped lid. Outside, walk the lot and the alley along the kitchen wall for one or two round or square lids set flush with the pavement. A box inside means an indoor trap. Lids outside mean an interceptor.
Indoor traps hide well. Some sit behind a rack of sheet pans that never moves, and some are recessed into the floor under a mat. Two lids in a line outside usually mark the inlet and outlet ends of one interceptor, not two tanks.
If the walk-around leaves doubt, paper usually settles it:
- The building’s plumbing plans, if the landlord or the last tenant kept them.
- The landlord or property manager, who often knows, since some leases put the interceptor on the owner.
- An old service invoice. A bill from a pump truck that lists hundreds of gallons was an interceptor, not an under-sink box.
Who cleans an indoor trap, and who pumps an interceptor?
An indoor trap holds little, so it fills fast and gets attention often, and in many kitchens staff or a service contractor handle it on a short cycle. An interceptor is a different job. Emptying a buried tank takes a vacuum truck and a pumping crew, the same kind of truck that pumps a home septic tank, and the questions worth putting to any pumper before hiring one work as well for a grease job.
Whether staff should touch the indoor box at all is a call for the kitchen and its landlord. An interceptor is never a kitchen task.
The kitchen sets the pace for either one, and the habits behind it are worked through in how fast a kitchen fills its grease trap. On the interceptor side, what a grease trap pump-out runs here is $175 - $450, by interceptor size and schedule.
Can a kitchen have both, and are they serviced on the same visit?
Yes. Some buildings run an indoor trap at the sink upstream of an outdoor interceptor. It often happens after a remodel, when a new fixture got its own trap and the interceptor out back stayed in place. The indoor box catches the first of the grease and the interceptor catches what gets past it.
Both can be handled in one stop. The truck pumps the interceptor from the lot, the crew deals with the indoor box on the same visit, and both go on one service entry with the condition noted. For a kitchen with both, that combined stop is how interceptor pumping on a standing schedule usually runs.
Does a Pocatello winter change how an outdoor interceptor is serviced?
Mostly it changes the walk to the lid. An interceptor lid sits flush with the lot, which in winter puts it right where the plow pushes snow, and a lid under a packed berm has to be dug out before the hose can go in. Meltwater that refreezes in the lid’s ring can also lock it in place. Below the lid, cold stiffens any grease that slips past the tank into the outside line.
Truck access is the other half. A vacuum truck has to park close enough for the hose to reach, across a lot that may be icy or full of parked cars at lunch. An early-morning or after-close visit, when the lot is empty, usually goes faster in January than one squeezed into the afternoon.
A few things make the winter visits go faster:
- Mark the lid with a tall stake or a flag before the first snow, so the plow driver and the crew can both find it.
- Tell whoever plows the lot to pile snow somewhere else.
- Keep a clear lane from the street to the lid, wide enough for a truck.