How does a grease trap work?

A grease trap is not added straight to the drain of the sink or appliance that it is filtering. There is a flow control valve that prevents the water from reaching the grease trap too fast before the trap itself. Also there is no real screen used to sieve the fat, oil ,grease and debris out of the water. The distance between the drains and the grease trap is particularly used to cool the water on its way to the trap. When the water is cooling, there are two ideas at work; the first is that food debris sinks, and the second is that fat, oil and grease floats. The flow regulates will keep the water from washing the debris from the trap during times of faster flow. The grease trap keeps the floating oils at the top of the water from passing through by making the water fill the well. There is a wall that travels down the well on the input side so that the water needs to pass under it to exit through the drain. The FOG is blocked from travelling to the drain by the wall and the larger food debris sinks to the bottom of the trap and cannot travel up to the drain on the other side of the wall.