Pipe reducers connect two pipes with different diameters. The two most common types are concentric reducers and eccentric reducers. Choosing the correct reducer type helps maintain flow stability, avoid air pockets or liquid accumulation, and meet the layout requirements of pumps, equipment and process lines.
What is a concentric reducer?
A concentric reducer has a centerline that remains aligned between the larger and smaller pipe ends. The shape is symmetrical, making it suitable for vertical piping and many general pipeline transitions where a centered flow path is acceptable.
What is an eccentric reducer?
An eccentric reducer has an offset centerline. One side of the reducer is flat while the other side tapers. This design is often selected for horizontal piping where engineers need to keep either the top or bottom of the pipe level.
Main differences
- Concentric reducer: symmetrical shape, centered transition, common in vertical lines.
- Eccentric reducer: offset shape, one flat side, useful in horizontal lines and pump suction piping.
- Flow layout: eccentric reducers help avoid trapped air or liquid pockets depending on installation direction.
When to use a concentric reducer
Use a concentric reducer when the piping layout requires a simple diameter transition and the centerlines of the connected pipes can remain aligned. It is common in vertical pipelines, process systems and many general industrial applications.
When to use an eccentric reducer
Use an eccentric reducer when the pipe bottom or pipe top must remain level. In pump suction lines, eccentric reducers are often installed to reduce the risk of air accumulation. The correct orientation depends on the fluid and engineering design.
How to specify a reducer
A complete reducer specification should include type, larger size, smaller size, wall thickness or schedule, material grade, standard and quantity. For example: ASME B16.9 eccentric reducer, NPS 6 x 4, SCH 40, ASTM A234 WPB.
Related products
See our pipe reducers page for concentric and eccentric options. You may also need pipe elbows, pipe tees and pipe flanges for the same piping system.
FAQ
Which reducer is better for pump suction?
Eccentric reducers are often preferred for pump suction lines, but final orientation should follow engineering design.
Do reducers need to match pipe schedule?
Yes, reducer wall thickness should match the pipe schedule or project specification for proper welding and pressure performance.
Need pipe reducers for an industrial project? Send your reducer type, size and material requirements to PipingFitting.com.