Grease traps. Every fast food person cringes at the thought of leaning and clearing the messy, mucky container. They remember the first time that they skimmed off the layer of crud to help the trap continue working.
Grease traps are, quite simply, a receptacle for grease and water to separate. The water goes back to the sewer system, while the grease stays in the grease interceptor. Unfortunately, most of the grease traps out there are manual systems which do not have much efficiency and must be cleaned by hand.
Let it go for too long, and there can be problems with the water supply and the city. Inspections go south, and not cleaning the grease trap turns into a civic nightmare. Not to mention, bad for business.
There are, however, automatic systems like the Thermaco big dipper which skim the grease on a pre-programmed schedule into a waste receptacle. Think of it like one of those automatic cat litter scoops where the grungy stuff is taken off the top to leave clean below.
The larger restaurants out there invest in these automatic systems so that they can better serve their customers. It's one less thing that they have to think about while they're getting ready for the shift. No sewage backups, no worries.
