I did some digging on this from an MEP parts perspective just recently but this was a problem identified with Revit 2020:
Release 2.16 was a major push to increase support for MEP components, but I haven’t a clear picture if there were restrictions on the older Revit APIs.
We have very limited instances where we branch our code by version, but we do target later versions for compatibility first.
If you can share a small sample file like the linked tread, we can take a closer look.
Ok let me break this out into a smaller Revit file and ill send the link for download.
Hey @jonathon , See link below and view to find pipe let me know if I can help in anyway.
https://arpis.sharefile.com/d-sc64c50ac6585430caf19124387f64e71
Looks like everything else is coming through could it be that since the pipe is sloped there is an issues on export? although the vent line above it which is the exact same family is sloped and coming through.
Hi @jonathon I updated to 2.18.0-rc left P&ID modeler disabled still drainage pipe not coming through see screenshot mark up below.
@jonathon no worries, I updated the small Revit file I sent you to 2023 and everything showed up in the export (screen shot below)
I will continue trying other things in Revit 2021 to try to get it to export I wouldn’t be surprised if it was a view setting that’s causing the pipe to not be exported.
I just concluded the same - Revit 23 is the stable on my testing machine and showed the total object count 243 as with the source revit file.
When a conversion/send occurs there is a success report available. Please feel free to share the one produced by Revti 2021. Sometimes the failed conversions give an explicit reason.
@jonathon When I change the system type of the pipe in the properties dialog box it exported one of the pipes it wouldn’t before, so I believe the problem lies within the system type I have in Revit. Don’t understand why that would be the case though.
This is very interesting - it could be similar to the other report where the query from the Revit API was previously incorrect. If I have time this week, I’ll investigate on that exact basis if you could the details to replicate.
Hello @B.Kaiser, I had the same problem and I use Revit 2024, and I tried Revit 2021 and the same thing happened to me, but in the pipes that had a slope. It can be two things, the first is that the elements in question were not selected, if you use the “by select” function, change to “by view” and place a view with all the elements that you want to export and that are visible, and then exports. If that doesn’t work like it did for me with pipes with slope, export in IFC (preferably version 4.0) and upload the file to speckle.
I am attaching the example of my export problem in case it is of any use to you.
https://app.speckle.systems/projects/32d0db5841/models/fb9b2a0848
I hope it helps. Greetings
Hola @B.Kaiser, yo tuve el mismo problema y uso Revit 2024, y probé con Revit 2021 y me pasó lo mismo, pero en las tuberías que tenían slope. pueden ser dos cosas, la primera es que los elementos en cuestión no se seleccionaron, si usas la función “by select”, cambia a “by view” y coloca una vista con todos los elementos que deseas exportar y que estén visibles, y luego exporta. Si eso no funciona como a mi con las tuberías con slope, exporta en IFC (preferiblemente en su versión 4.0) y sube el archivo a speckle.
Te adjunto el ejemplo de mi problema de exportacion por si te sirve de algo.
https://app.speckle.systems/projects/32d0db5841/models/fb9b2a0848
Espero te sea de ayuda. Saludos
@Alvaro_Suarez are you saying that only importing an IFC made from Revit 2024 allowed for the piping systems to get to Speckle, I think i’m not fully understanding.
@jonathon
Yes, apparently it worked for me. but it destroyed the toilets in that link I shared 
I exported an IFC 4.0 (better behavior of objects with curved and theoretically lighter bodies) from Revit and uploaded that file to speckle.
Similar things have also happened to me with HVAC electrical elements and custom structural connections without grouping into connection type elements (single bolts and cutouts for example) and strange things with walls in different phases (with fillings from a window removal for example) , I have solved it either with a route from IFC to Speckle or sometimes it looks better from Revit using the connector. I’ll try to see which one looks better and has less data loss.
si, aparentemente, a mi me funcionó. pero destruyó los inodoros en ese link que compartí
exporté un IFC 4.0 (mejor comportamiento de objetos con cuerpos curvos y en teoría mas ligeros) desde Revit y ese archivo lo subí a speckle.
Tambien me ha pasado cosas similares con elementos eléctricos de HVAC y Conexiones estructurales personalizadas sin agrupar en elementos tipo conexión (planchas pernos y recortes solos por ejemplo) y cosas raras con muros en fases distintas (con rellenos de una remoción de una ventana por ejemplo), lo he resuelto o bien con una ruta desde IFC a Speckle o a veces queda mejor desde el Revit usando el conector. Tanteo a ver cual tiene mejor pinta y menor perdida de data.
It is from Revit 2021, in the link you will see that it has an IFC origin in the most recent version and the previous version in an RVT 2021
Es de Revit 2021, en el link vas a ver que tiene en versión mas reciente un origen de IFC y la versión anterior en un RVT 2021
Right - I was confused by your first line, which said you were using 2024.
I think we have a settled opinion that we are doing a better job from 2024 than from 2021 aided by improvements int he Revit API
Hello @jonathon I have the same problem, when I export from Revit 2021 to speckle, the pipes withe the “domestic cold water”, “domestic hot water”, “sanitary” and “undefined” systems are missing. Then when I change the system to any other, it shows up.
https://app.speckle.systems/projects/947aba3e2e/models/16ee9c9197
Hey @OrlandoRosas ,
Welcome to the community! Feel free to Introduce yourself 
to the community if you want to! 
Sorry to hear you are having issues exporting pipes. Can you please share the Revit file with us so we can try to reproduce the issue? FYI, we released the next generation of our Revit connector. This is the new version of our Revit connector and we are actively working on improving this version. Can you try downloading that and see if this issue still persists?
Hi @gokermu, thanks for the welcome!
I just tried the Revit connector, but the issue still persist. Maybe there’s something I’m missing.
I’m working with Revit 2021.
This chat doesn’t allow me to upload the revit file as an attachment, so I share it in a WeTransfer link:
https://app.speckle.systems/projects/947aba3e2e/models/16ee9c9197
As is often reported, Revit 2021 MEP support within the Revit API is inferior. We have made all the improvements we can, but some elements are poorly served.
By demonstration, your file sent from Revit 2024 shows a complete conversion.
