I understand there are a lot of variables to something like this, so I'm going to try to provide enough detail that people can at least understand the question here:
I have a washer/dryer I'd like to relocate to my garage. There is already a hot/cold PEX supply exposed in the garage, which runs up to supply one sink and one shower in a finished room (no other fixtures). There is also a 3" drain running from that room. Is it possible to tap into both the supply and drain lines with branches running along ceiling/wall and down to desired washer location as shown in the marked-up photo?