When the outflow from the kitchen sink enters the grease trap, the solid food particles sink to the bottom, while lighter grease and oil float to the top. The relatively grease-free water is then fed into the normal septic system. The food solids at the bottom and floating oil and grease must be periodically removed in a manner similar to septic tank pumping. A traditional grease trap is not a food disposal unit. Unfinished food must be scraped into the garbage or food recycling bin. Milkshakes, gravy, sauces and food solids must be scraped off dishes before entering the sink or dishwasher.