Vertical Heater Treaters are used in the Oil and Gas industry to help facilitate crude oil/water separation by speeding up emulsion separation through applying heat. Heater Treaters can be thought of as low pressure, three-phase separators that are equipped with fire tubes. They separate gas from the incoming emulsion and separate the emulsion into a water phase and an oil phase. Heater treaters can also function as a free-water knockout, a heat exchanger, a filter, and a water wash tan.