Air Elimination FPP Air Eliminators function on a gravity principle, and are normally installed on top of the FPP Strainer. In systems with little or no back pressure, either a back pressure valve or an air check valve may be required to enhance the efficiency of the air eliminator. On higher viscosity liquids such as diesel fuel, the air may not have enough time to rise during passage of a standard strainer. For use on higher viscosity liquids, a high capacity strainer with greater holding capacity is available. Please consult with your distributor to determine whether a high capacity strainer is required. Air Eliminators Shown   For LPG service, a vapor eliminator with pressure relief valve is used, in conjunction with a differential pressure check valve on flow meter outlet.