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Eccentric reducer dimensions refer to the key measurements—such as inlet and outlet diameters, center-to-end length, and wall thickness—that define how these fittings connect pipes of different sizes in a piping system.
Unlike concentric reducers, an eccentric pipe reducer has an offset centerline that keeps one side flat. This unique shape ensures uninterrupted flow and prevents air pockets or fluid buildup—especially in horizontal pipe runs.
Whether you’re designing industrial process lines, pump suction systems, or commercial plumbing layouts, choosing the right eccentric reducer size is essential for system efficiency, flow control, and equipment protection.
In this guide, we’ll break down the most common eccentric reducer dimensions, their real-world applications, and how to choose the right fitting using charts and specifications.
An eccentric reducer is a pipe fitting that connects two pipes of different diameters. But unlike a concentric fitting (which tapers evenly like a cone), the eccentric fitting has one side flat. This design keeps the bottom of the pipe level, so air or liquid doesn’t get trapped.
You’ll often see eccentric reducers in horizontal pipe runs. Why? Because they stop gas bubbles from collecting at the top (when installed flat side up) and let water drain properly (when installed flat side down).
Choosing the right eccentric reducer dimensions is not just about matching pipe ends. It’s about:
That’s why understanding eccentric reducer sizes—and how they behave in different systems—is crucial.
| Reducer Size | DN Size Range | Standard Thickness | Typical Applications | Common Materials |
| 10 x 8 | DN250 → DN200 | Sch40, Sch80 | Suction lines of large centrifugal pumps; Process piping in oil refineries and chemical plants | Stainless Steel 304/316, Carbon Steel |
| 8 x 6 | DN200 → DN150 | Sch40 | Cooling water lines in HVAC systems; Water treatment plants; Industrial piping for slurry or chemical fluids | Stainless Steel, Galvanized Carbon Steel |
| 6 x 4 | DN150 → DN100 | Sch40, Sch80 | Fire protection systems; Compressed air or nitrogen pipelines; Clean process water | SS304/316, PVC, Carbon Steel |
| 6 x 3 | DN150 → DN80 | Sch40 | Filtration skid connections; Drainage and blowdown lines; Skid or pump base systems | SS316, Carbon Steel |
| 6 x 2 | DN150 → DN50 | Sch40 | Sampling lines; Maintenance bypasses; Control valve bypass connections | 316L Stainless Steel, PVC, PTFE-lined |
| 4 x 3 | DN100 → DN80 | Sch40 | HVAC chilled water discharge; Secondary distribution piping; Utility lines in commercial buildings | SS304, Carbon Steel, Copper |
| 4 x 2 | DN100 → DN50 | Sch10s (Copper), Sch40 (Steel) | Connecting mains to smaller service lines; Irrigation and plumbing systems; Washdown or utility water feeds | Copper, PVC, Stainless Steel |
| 3 x 2 | DN80 → DN50 | Sch40 | Labs and pilot plants; Food and beverage pipelines; Steam and condensate lines | SS316L, Carbon Steel, Copper |
Eccentric reducers come in many sizes, but some dimensions show up again and again across industries. These “top picks” aren’t random—they’re driven by real-world system designs and flow requirements.
Let’s walk through 8 of the most common eccentric reducer sizes, and I’ll explain what each size does best, where it’s often used, and why engineers and contractors love them.
Size: 10″ to 8″ (DN250 → DN200)
Standard Thickness: Sch40, Sch80
Popular Materials: Stainless steel 304/316, Carbon steel
Typical Use:
Why it’s common:
This is a go-to size for mainline flow reduction without sudden pressure drops. At this scale, systems demand stable flow and minimal turbulence—this size hits the sweet spot.
Best for: Often used in heavy-duty flow control systems. Commonly stocked in ANSI B16.9 standards. Ideal for upstream/downstream projects with short lead time requirements.
Size: 8″ to 6″ (DN200 → DN150)
Standard Thickness: Sch40
Popular Materials: Stainless steel, Galvanized carbon steel
Typical Use:
Why it’s common:
It’s widely used in medium-scale piping systems. It offers efficient flow control and fits well in compact spaces without compromising velocity.
Tip: High turnover size. Frequently used in municipal and commercial mechanical systems. Usually available from stock—quick to ship.
Size: 6″ to 4″ (DN150 → DN100)
Standard Thickness: Sch40 / Sch80
Popular Materials: SS304/316, PVC for water, CS for air
Typical Use:
Why it’s common:
This size is perfect for distribution branches where you don’t want a pressure spike. It’s easy to source and fits most pump systems.
Pro Tip: One of the most commonly ordered reducers. Fits general-purpose pipe layouts. Easy to find with short lead time across suppliers.
Size: 6″ to 3″ (DN150 → DN80)
Standard Thickness: Sch40
Popular Materials: SS316, Carbon steel
Typical Use:
Why it’s common:
It allows for quick pressure reduction in supporting systems. It’s compact and fits well in tight skids or pump bases.
Note: A practical solution for size transitions within small skids or containerized systems. May require confirmation on material availability depending on project spec.
Size: 6″ to 2″ (DN150 → DN50)
Standard Thickness: Sch40
Popular Materials: 316L stainless, PVC, PTFE-lined (corrosive systems)
Typical Use:
Why it’s common:
This is often used in precision flow applications where a big pipe needs to feed into a very small one.
Use with care: Sharp reduction can create turbulence—use eccentric to smooth it out and keep the bottom aligned.
Size: 4″ to 3″ (DN100 → DN80)
Standard Thickness: Sch40
Popular Materials: SS304, Carbon steel, Copper (for plumbing)
Typical Use:
Why it’s common:
It’s widely available and fits many modular piping systems. Excellent balance between flow control and pressure regulation.
Best for: Widely available and frequently used in building engineering projects. Also stocked in copper for plumbing-grade installations.
Size: 4″ to 2″ (DN100 → DN50)
Standard Thickness: Sch10s (for copper), Sch40 (for steel)
Popular Materials: Copper, PVC, Stainless steel
Typical Use:
Why it’s common:
Perfect for industrial water networks where flow must reach multiple small lines.
Best for: A go-to for plumbing and utility projects. Make sure to specify thread/weld ends clearly when placing the order.
Size: 3″ to 2″ (DN80 → DN50)
Standard Thickness: Sch40
Popular Materials: SS316L (for hygiene-critical systems), CS, Copper
Typical Use:
Why it’s common:
Compact, easy to install, and very versatile. Small but mighty—this size works well when flow must be reduced to match instruments, valves, or smaller sections.
Best for:Popular in precision piping and modular systems. Confirm hygienic-grade requirements if used in FDA/food applications.
Bonus Tip: Use a Size Chart
When in doubt, an eccentric reducer size chart helps compare outer diameters, schedules (like Sch40, Sch80), and center-to-end dimensions. But don’t just rely on a chart—match it to your real-world conditions and consult your system’s flow requirements.
Choosing the right eccentric reducer dimensions is essential for a smooth installation and reliable pipeline performance. Below is a clear, practical guide for selecting the right eccentric pipe reducer based on real project requirements.
Always confirm the exact outer diameters of the two pipes you’re connecting.
Check the wall thickness (e.g. Sch40, Sch80) to match reducer ends accurately.
Refer to an eccentric reducer size chart to avoid mismatch.
In horizontal liquid pipelines, use eccentric fittings with the flat side on top. This prevents air pockets and pump cavitation.
In horizontal gas or steam pipelines, install with the flat side on the bottom to allow liquid drainage.
For vertical pipelines, concentric fittings are often more suitable.
Some pipelines have limited vertical or horizontal space.
Eccentric reducers take up less space than concentric types.
Check center-to-end dimensions if you are working in a compact area.
The type of medium determines the best eccentric reducer size and design:
Clean water or general fluids: both reducer types may work
Sludge, slurry, or oil: eccentric reducers perform better, especially in horizontal lines
Compressed air or steam: flat side orientation matters to prevent flow issues
For pump suction lines, always use an eccentric fitting with flat side on top to eliminate air entrapment.
Before a control valve, flat side down helps with proper fluid evacuation.
Allow straight pipe lengths between pumps and reducers when possible.
Choose materials based on the media and system pressure:
| Application | Recommended Material |
| General water / HVAC | Carbon Steel / SS304 |
| Corrosive chemical flow | SS316 / Duplex / PTFE-lined |
| Food & pharma | SS316L with sanitary finish |
| Fire systems / oil lines | Carbon Steel Sch40 / Sch80 |
| Residential plumbing | Copper / PVC (check codes!) |
Ensure the reducer complies with ASME B16.9, DIN 2616, or EN 10253 depending on your region.
Check if the project requires butt-weld, socket weld, or threaded ends.
Ask the supplier for data sheets or dimension drawings if needed.
Eccentric reducers do more than just connect pipes—they manage flow, reduce system stress, and ensure long-term efficiency.
So the next time you spec out a project, be sure to evaluate the dimensions of eccentric reducer fittings carefully. These dimensions directly impact compatibility, performance, and installation ease.
Use resources like an eccentric reducer size chart or a professional sizing guide to verify outer diameters, wall thickness, and end-to-end measurements. And when in doubt, consult an expert who understands how eccentric pipe reducers perform across various industries and systems.
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