My experience is more with the "galley" for leaks, either from the drain or the supply copper plumbing, but here is some basic information you could supply to get better help:
- Is your trailer the rear bathroom or side?
- Can you post any photos of the area where you feel the problem is?
The copper supply pipes are soldered on my trailer. The drain pipes are a larger-diameter black plastic, glued together. Both types require cutting, removal, and replacement, if they are like my '74 Sovereign
Same type of plumbing as your home bathroom sink. Have you done any plumbing at home?