Grease traps intercept any oil or grease from the flow of water leaving your sink (or dishwasher). When the mixture of water and grease enters the trap, it begins to cool. As it cools, the grease and oil separate out of the water and rise to the top of the grease trap. The water continues flowing, eventually leaving the grease trap while the grease and oil remain inside. You will need to clean the grease and oil out when your grease trap gets around half full.
Grease traps and Grease trap accessories can be found at www.supplyhouse.com