Grease traps have been used since Victorian days: Nathaniel Whiting obtained the first patent in the late 1800s. The traps reduce the amount of fats, oils and greases (FOGs) that enter sewers. They comprise boxes within the drain run that flows between the sinks in a kitchen and the sewer system. They only have kitchen waste water flowing through them, and do not serve any other drainage system, such as toilets. They can be made from many different materials, such as stainless steel, plastics, concrete & cast iron. They range from 35 liter capacity to 45,000 liters and greater. They can be located above ground, below ground, inside the kitchen or outside the building.