<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> A grease trap (also known as grease interceptor, grease recovery device and grease converter) is a plumbing device (a type of trap) designed to intercept most greases and solids before they enter a wastewater disposal system . Common wastewater contains small amounts of oils which enter into septic tanks and treatment facilities to form a floating scum layer . This scum layer is very slowly digested and broken down by microorganisms in the anaerobic digestion process . Large amounts of oil from food preparation in restaurants can overwhelm a septic tank or treatment facility, causing release of untreated sewage into the environment . High - viscosity fats and cooking grease such as lard solidify when cooled, and can combine with other disposed solids to block drain pipes . </P> <P> Grease traps have been used since Victorian days . Nathaniel Whiting obtained the first patent for a grease trap in the late 1800s . These reduce the amount of fats, oils and greases (FOGs) that enter sewers . They are boxes within the drain run that flows between the sinks in a kitchen 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 . </P>

What is the purpose of a grease trap