Grease Trap vs Grease Interceptor: What Is the Difference?

Short answer: size and location. A grease trap is small and sits indoors under or near the sink. A grease interceptor is large and sits outside, usually underground. They do the same job, which is stopping fat, oil and grease from reaching the sewer. The scale is what changes. Here is how to tell which you have, and which you need.

Grease traps, small and indoor

A grease trap is the smaller unit, usually under 100 gallons, installed under a sink or in the kitchen. Because it is small, it fills quickly and needs cleaning often, sometimes monthly for a busy kitchen. It suits cafes, small takeaways and lower-volume sites.

Grease interceptors, large and outdoor

An interceptor is the larger unit, often 500 gallons or more, installed underground outside the building. It handles far more wastewater, so it is serviced less often, commonly quarterly. Busy restaurants and high-volume kitchens use these because a small indoor trap could not keep up.

Which one do you need

That comes down to your output and your local rules. A trap should be sized to handle a set share of your daily wastewater flow, and your water authority approves the right type and size for your operation when you set up your trade waste agreement. Under-size it and you will be cleaning constantly and still breaching limits.

How the difference changes your cleaning

The bigger the unit, the more it holds and the more it costs per pump-out, but the less often you need one. A small trap is cheap per visit and frequent. A large interceptor is dearer per visit and rarer. Either way, the 25% rule still decides the timing.

The bottom line

Trap means small and indoor, interceptor means large and outdoor, and both keep grease out of the sewer. Your kitchen's volume and your water authority decide which you run, which sets how often and how much you clean.

Not sure what you have or what it needs? Compare quotes from licensed operators. Related: how often to clean and cleaning costs.