What is a grease trap? Does it replace the standard trap below a sink? When or where is it necessary?

Grease trap does not replace regular trap under the sink. Read Wikipedia definition of Grease Trap.

Grease trap - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Grease_trap)

A is required a septic tank installations. Both the kitchen sink and the washing machine are tied into a single line that goes and then to the septic tank. The reason for this is that the grace Filter out garbage and grease from the sink and went from the washer so the date does not clog the drain field. On a single dwelling the grease trap is located in the ground outside the house. In multiple dwellings is located under the sink. Does this answer your question? Good luck, Tom

Grease trap is a metal or plastic tank where the grease (oil, fat) from your cooking will get separated from dishwasher where the water going out into the sewer. Because of law

http://www.newtonma.gov/civicax/filebank/documents/35874