Grease traps are designed to intercept the grease and solid waste from a water drainage system, before it enters the sewer system. Essentially a grease trap works by separating the different waste products that have been washed down the drain, and sorts them into different compartments based on their viscosity.
Most waste contains small amounts of oils and other chemicals; which enter into a septic tank or treatment facility, where they are slowly broken down by micro organisms in the waste water. While smaller amounts of waste can be easily managed; larger amounts such as grease and waste by products from commercial kitchens, hospitals and factories are a little different. If allowed to enter into the sewer system, these will eventually cause a blocked drain or pipe, and can even cause contamination of another water supply.