A Treater is a separator vessel with a heat source immersed in the liquid fluid phase to help separate water and gas from oil-water emulsions. The heat source is usually a firetube but can also be electric elements or steam coils. Treaters can be Horizontal or Vertical and have an integrated free water knockout section to remove any non-entrained water. Removing the water will help reduce the fuel consumption. Treaters may also incorporate mechanical separation aids like coalescing packs or electrical grids to enhance the separation. Treaters are typically designed for preparing the oil for sales.