The waste oil is heated to a temperature of 105 °C in the lower section of the column. Here, the water evaporates and is pumped away after it condenses. After reaching the appropriate temperature, the oil is transported through pipes to the upper part of the column, where the remaining water vaporises. For optimal dewatering, a defined level is required in the column. As the oil surface is very turbulent due to the action of pumps and heating, making level measurement directly inside the column practically impossible. For that reason it is done in a bypass tube.