A grease trap is a small reservoir built into wastewater piping a short distance from the grease producing area (typically the kitchen area). It is designed for the purpose of removing fats, oils, and grease and preventing them from entering the sanitary sewer system. Baffles in the grease trap reservoir hold the wastewater long enough for the grease to congeal and rise to the surface. The grease can then be removed and disposed of properly. View grease trap animation.