Julie B888,
Not sure if I can help you but let's maybe try to clear up some terminology here. The connection between the two pipes are called the joint. If the pipes are PEX, there are no "seams".
What brand of rv is this and the age? Forget about silicone of any sort to repair the leak. If you do find silicone where the leak is, someone has done a hokey bandaid temporary repair at best. A thought that came to me is that the piping might have frozen at some point and has compromised the joint where the pipes come together. If the pipe is pex maybe the metal crimp piece has loosened and is causing a leak. If that's the case then you need to go to Home Depot or an rv place and get a Flair-It or Shark Bite fitting and replace the old leaking one. First things first, what rv are we talking about and it's age? Are the pipes some plastic type material or is it metal?