The AG Air Gap Fitting is used for indoor installations of Model 375, 375A, 475, 475V, and 975XL Reduced Pressure Principle Backflow Preventers for the connection of a drain pipe to the backflow preventer, directing nuisance water discharge to a safe drain. The AG Air Gap Fitting can be mounted to the body of any drain line made of any standard piping material. The AG prevents a cross connection between the drain and potable water supply. Materials include an epoxy-painted cast grey iron elbow and zinc-plated steel bolts for long-lasting effectiveness.