# Concentric reducer

> Butt-weld concentric reducers to ASME B16.9 in ASTM A234 WPB and A403, joining two pipe sizes on one centerline, with the request details needed to quote them.

URL: https://jjprojectsok.com/products/steel-structural/concentric-reducer  
Español: https://jjprojectsok.com/es/products/steel-structural/concentric-reducer  
Updated: 2026-10-16

Butt-weld fitting that joins two pipe sizes on a common centerline.

**In short:** Butt-weld fitting that joins two pipe sizes on a common centerline. JJ Projects sources it to the specification the buyer names. Typical reference, standards: ASME B16.9.

## Specification references

- Standards: ASME B16.9
- Materials: ASTM A234 WPB (carbon), A403 (stainless)
- End connections: Beveled ends for butt welding
- Size: Large and small NPS, with wall schedule for each end

> Typical references only. The governing specification is the one on your purchase order or datasheet.

## Typical uses

- Changing line size on vertical runs and in racks
- Matching pipe size to equipment nozzles and valves
- Transitions after pumps and in headers
- Stainless and alloy piping where a size change is needed

## What to include in a request

A request with these details can be quoted without a round of questions. Send what you have and we will ask for the rest.

1. Large-end NPS and small-end NPS, for example 8 x 6
2. Wall thickness or schedule for each end
3. Concentric or eccentric type
4. Material and grade, for example ASTM A234 WPB or A403 WP316L
5. Seamless or welded construction, if the specification allows both
6. Quantity
7. Documents: material test report and any examination or marking requirement

[Request this item](https://jjprojectsok.com/request-a-quote?item=concentric-reducer)

## Questions

### When is an eccentric reducer used instead of a concentric one?

An eccentric reducer keeps one side of the pipe flat. It is common on pump suction lines, with the flat side up, to avoid trapping vapor, and on horizontal lines where the bottom must stay level for drainage. A concentric reducer keeps both ends on one centerline.

### Do I need to give the schedule at both ends?

Yes. Each end is beveled to match the pipe it welds to, so the large end and the small end may have different wall thicknesses. State both.

## Related items

- [90° long radius elbow](https://jjprojectsok.com/products/steel-structural/elbow-90-lr): Butt-weld 90 degree long radius elbows to ASME B16.9 in ASTM A234 WPB and A403, and what a fittings request needs to be quoted, by NPS and schedule.
- [Equal tee](https://jjprojectsok.com/products/steel-structural/equal-tee): Butt-weld equal tees to ASME B16.9 in ASTM A234 WPB and A403, sized by NPS and schedule, and what to include in a request for equal tees so it can be quoted.
- [Seamless pipe](https://jjprojectsok.com/products/steel-structural/seamless-pipe): Seamless carbon and stainless pipe by NPS and schedule, sourced to ASTM A106, A312 and API 5L, with the details a pipe request should carry.
- [Centrifugal pump](https://jjprojectsok.com/products/electrical-instrumentation/centrifugal-pump): Centrifugal process pumps to API 610 and ASME B73.1, supplied to your datasheet, and what a request needs: fluid, flow, head, NPSH available and materials.

## Guides

- [Pipe schedules: NPS, OD and wall thickness](https://jjprojectsok.com/knowledge/pipe-schedules-explained): NPS is a label, not a measurement. Learn how pipe schedule sets wall thickness under ASME B36.10M and B36.19M, with OD and wall tables for NPS 2, 4, 6 and 8.
- [Material test reports (MTRs) and EN 10204](https://jjprojectsok.com/knowledge/material-test-reports): What a material test report contains, how EN 10204 types 2.1, 2.2, 3.1 and 3.2 differ, what heat numbers mean, and what to check against the purchase order.

[All steel and structural](https://jjprojectsok.com/products/steel-structural)