Table of content
Introduction
The applications of concentric and eccentric reducers in pipe installation systems are different. Although both are used to connect two pipes of different sizes, the specific use depends on the direction of the pipe. Usually, concentric reducers are mostly used for vertical pipes, while eccentric reducers are mostly used for horizontal pipes. I will introduce the specific differences in detail below.
What Is a Concentric Reducer?
A concentric reducer is a pipe fitting with different diameters at both ends, and its shape is conical. The centerline is on one diameter. This allows fluid or gas to flow evenly from one end to the other.
Main Features:
- The centerline is the same
- The object flows evenly
- Suitable for vertical installation
What Is an Eccentric Reducer?
Eccentric reducers are also used to connect two pipes of different diameters. The centerline is not on a straight line, and one end is offset from the center. This makes one end flat and the other end curved.
This design is mostly used in horizontal pipe installation, and the downward end can be used as a flat surface, so that fluid or gas will not accumulate.
Main Features:
The centerline is offset, and there will be no accumulation at the bottom when installed horizontally.
Visual Difference at a Glance
| Feature | Concentric Reducer | Eccentric Reducer |
| Shape | Cone-like, symmetrical | Asymmetrical with one flat side |
| Centerline | Shared between both pipe ends | Offset centerlines |
| Flow type | Even, centralized | Bottom/top flow control |
| Best for | Vertical piping | Horizontal piping and pumps |
When to Use a Concentric Reducer
Concentric reducers are often used in the following situations:
1. Vertically installed pipes.
2. Objects that are not prone to accumulation.
Common applications:
- In industrial pipes.
- In pipe systems without sediment accumulation.
- In air or gas pipes.
- Concentric reducers are suitable for vertical or sediment-free pipes.
When to Use an Eccentric Reducer
- In horizontal pipe systems.
- In objects that are prone to sedimentation.
- Near the pump suction port, cavitation can be avoided.
Common Applications
- Near the pump inlet
- Horizontal piping systems
- Sloped drainage piping systems
Pros and Cons
Concentric Reducer
Pros:
- Even flow
- Easy to make
- Used in vertical pipes
Cons:
Will cause accumulation in horizontal pipes
Eccentric Reducer
Pros:
- Mostly used in horizontal piping systems
- Can prevent cavitation
- Easy to make
Cons:
Uneven flow rate in vertical piping systems
Installation Best Practices
| Reducer Type | Orientation | Use Case Example |
|---|---|---|
| Concentric | Vertical pipe run | Connecting vertical pump discharge |
| Eccentric (flat up) | Horizontal pipe suction (pumps) | Prevent air entrapment |
| Eccentric (flat down) | Drainage flow | Promote full liquid drainage |
If installed incorrectly, it may cause uneven flow rate or gas accumulation. Therefore, when installing, be sure to pay attention to whether it is installed horizontally or vertically.
Materials and Sizes
The materials that can be used to make reducers are:
- Carbon steel
- Stainless steel
- Alloy steel
- Copper
- PVC or CPVC
- HDPE
Sizes:
The size range can be from ½” to 48″. The specific production size may vary according to different standards. Please refer to ASME, ASTM, JIS or ISO for details.
Real-World Examples
| Application | Reducer Type | Why? |
|---|---|---|
| Fire sprinkler riser | Concentric reducer | Vertical flow — symmetry preferred |
| Pump inlet in water plant | Eccentric reducer | Flat top to avoid air lock |
| Horizontal waste pipe | Eccentric reducer | Flat bottom for full drainage |
| Gas supply to vertical tank | Concentric reducer | Balanced, centered flow required |
Summary
For those who work in industrial piping, it is important to understand the difference between concentric reducers and eccentric reducers, because incorrect installation may cause poor flow performance, accumulation and other troubles.
