# Best IFC classification for a reducing coupling

**URL:** <https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963>\
**Category:** IFC\
**Tags:** ifc\
**Created:** [February 22, 2025, 5:30pm UTC](https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963 "2025-02-22T17:30:19Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![namio.sousa](https://avatars.discourse-cdn.com/v4/letter/n/ce7236/32.png) [@namio.sousa](https://forums.buildingsmart.org/u/namio.sousa)\
**Post date:** [February 22, 2025, 5:30pm UTC](https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963/1 "2025-02-22T17:30:19Z")

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The IfcPipeFittingTypeEnum gives us the value _CONNECTOR_ to classify a coupling used to join two pipe segments. However, if I have a _ **reducing coupling** _ made of the same material (PVC), should it still be classified as a _CONNECTOR_, or may I classify it as a _TRANSITION_, since it is a fitting with two ports of different sizes? Which is the best classification?

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**Author:** ![ejs](https://avatars.discourse-cdn.com/v4/letter/e/3d9bf3/32.png) [@ejs](https://forums.buildingsmart.org/u/ejs)\
**Post date:** [February 24, 2025, 7:47am UTC](https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963/2 "2025-02-24T07:47:11Z")

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I think TRANSITION makes more sense if the nominal diameter changes. I would think of COUPLING as an element with the same nominal diameter on all sides.

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**Author:** ![marko.ripatti](https://avatars.discourse-cdn.com/v4/letter/m/bbce88/32.png) [@marko.ripatti](https://forums.buildingsmart.org/u/marko.ripatti)\
**Post date:** [February 26, 2025, 2:15pm UTC](https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963/3 "2025-02-26T14:15:03Z")

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MagiCAD uses TRANSITION in such cases both in ventilation and piping side.

 ![image](https://us1.discourse-cdn.com/flex016/uploads/buildingsmart1/original/2X/1/1b11e24f47ad2a93b2e14372c03d322eee334729.png)

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**Author:** ![namio.sousa](https://avatars.discourse-cdn.com/v4/letter/n/ce7236/32.png) [@namio.sousa](https://forums.buildingsmart.org/u/namio.sousa)\
**Post date:** [March 11, 2025, 3:40pm UTC](https://forums.buildingsmart.org/t/best-ifc-classification-for-a-reducing-coupling/5963/4 "2025-03-11T15:40:31Z")

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Thanks @ejs and @marko.ripatti.