Fuzion 315 question

[Wares94]

We are getting ready for our 1st trip in our new camper, so I was checking everything out making sure we were good to go and I noticed a small keyed door on the door side of the camper. I opened it and there is what looks like a fill hose with a rubber cap on it, I don't know what it is for. Anyone have any ideas what it might be for?

[tileman]

We have a fuzion 310 and on the left side facing the trailer is our fresh water fill. Its behind a keyed door with a black rubber cap.
This is not mine but the same setup kind. https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcQA41LGtX4FXCCGtxFzGtAUE1521hz2m BrQhtMfsdB85zZktd0yAA

[Wares94]

Thanks, That's it because the 310 and the315 are basically the same trailer.

2013 Fuzion 315
2007 Dodge 2500 4x4 diesel
2006 Club Car