A DI reducer, or ductile iron reducer, is a type of fitting used in plumbing and piping systems to transition between pipes of different diameters. Its primary function is to reduce the diameter of a pipe section, facilitating the flow of fluids from a larger pipe to a smaller one or vice versa. DI reducers typically feature a conical or tapered design, gradually decreasing in diameter along their length. This design helps to minimize turbulence and pressure losses within the piping system, ensuring efficient fluid flow.