I have a set of north side bathrooms and a set of south side bathrooms. The north side bathroom is a single bathroom that is ADA compliant. The south side bathrooms are for multiple use at the same time. Similar to my last module for the HVAC systems - my biggest challenge with the plumbing systems was that I had to make sure it matched the outer envelope of the building. I couldn't just do a system that would flow along a vertical pipe directly - I had to model the connection between each floor and make sure that it lined up. The other big challenge was that my toilet was very cramped. I didn't know that the piping would take up so much space and that the connections required extra space so that the pipes can bend. That was finnicky as well and I had a lot of trouble connecting every single toilet. While there are some toilets that aren't connected, it's a lesson learned that I will definitely model with more space in mind next time. While I tried my best to make sure that my pipes didn't clash with the outer envelope of the building, I still couldn't make it work perfectly. You can see in the BIM360 merged model (https://model.b360.autodesk.com/projects/a7e86ce2-2b4b-4375-a361-61cdec24a3b7/model-set/a1a179a4-2a68-467d-aae4-a7d8b603dc79/viewer/models) that there are some clashes. Again, this will be taken as a lesson learned to give toilets more space and also it's probably better to put them where there aren't as many constraints).
For my ADA compliant bathroom, it was easier to model. There was a lot more space for the pipes and the elements to join - as you can see in the pictures below, there were no clashes between any of the piping and architectural elements.