Which piping component changes the pipe size from larger to smaller?

• A. Reducer
• B. Flange
• C. Tee
• D. Elbow

Answer: (A)

When a piping system needs to transition from a larger diameter to a smaller diameter, a reducer is used. A reducer has one end larger and the other end smaller, allowing a smooth change in size so the flow can continue into the smaller pipe. Reducers can be concentric, keeping the centerline aligned, or eccentric, which shifts the alignment to suit horizontal runs and avoid flow issues near the joints.

Understanding how it affects flow helps: narrowing the bore increases fluid velocity and causes a pressure drop across the fitting, so proper selection helps manage these effects and maintain downstream performance.

A flange is a joint face that connects pipes without changing their size. A tee adds a branch and splits flow, and an elbow bends the pipe while keeping the same diameter. Thus, the component that changes pipe size from larger to smaller is the reducer.