A grease trap is a device that wastewater flows through prior to entering your city’s sanitary sewer system. The device traps Fats, Oils and Greases (FOG), preventing it from flowing into the sewer line and clogging it. When the wastewater goes through the grease trap, the FOG rises to the surface and floats on top of the water, while the solids sink to the bottom. The FOG is then trapped inside the grease trap while the rest of the water exits to the sewer line.