Vertical Heater Treater The most commonly used single-well treater is the vertical heater-treater . The vertical heater-treater consists of four major sections: Gas separation Incoming fluid enters the top of the treater into a gas separation section, where gas separates from the liquid and leaves through the gas line. . If the treater is located downstream of a separator, the gas separation section can be very small. The gas separation section should have an inlet diverter and a mist extractor. Free-water knockout The liquids flow through a down-comer to the base of the treater,which serves as a free-water knockout section. If the treater is located downstream of a free-water knockout or a three-phase separator, the bottom section can be very small. If the total well stream is to be treated,this section should be sized for 3 to 5 minutes’ retention time to allow the free water to settle out. This will minimize the amount of fuel gas needed to heat the liquid stream risi