The combo is called a 'wet bath.'
Pull lightly on the pipe. Has it come off the toilet? That can happen to any connection if you blow the system with too much pressure (more than 40 or 60 psi). If you can't easily see the leak, you'll have to pull the toilet. It's real easy:
- If you can, drain and flush the black tank
- Pressureize the RV by having a fan blow fresh air in.
- Turn off the water and reveive the pressure in the line (no problem for you
- Flush the toilet to remove water from the bowl
- Evenly loosen the two bolts holding the toilet to the floor
- Carefully pull the toilet straight up off the bolts. Be sure not to strain the fresh waterline too much. Oh, and don't loose the bolts down the drain.
You won't need to replace the gasket if it looks good since it isn't that old. They are rubber, not beeswax like a home toilet.