This is a timely thread. On our last camping trip we arrived and right away my wife noticed a huge pool of water on the floor while setting up. I quickly discovered that the trap below the kitchen sink had come completely undone and separated and the water poured down the sink was flowing straight onto the floor!
It didn't take much time to put it all back together and have it tightened up properly again with no further leaks. Biggest trouble was cleaning up the mess of water. I ended up checking all the other connections as well as was able to add a little extra tightening to most.
Bought the trailer new in 2011 and don't believe I'd ever tightened any of the plumbing connections until this disaster. Definitely will be checking them periodically. With all the driving and washboard gravel roads we've been on I'm not surprised that things have loosened up.
As an additional anecdote, when I bought this trailer I added one of those child/pet grates to cover the bottom of the screen door. It has one screw in it that keeps the vertical bars centred in the middle of the assembly. Each time we arrive at our new destination that screw has completely backed itself out, no matter how much I'd tightened it up since the last episode. Vibration can really cause threaded items to loosen, so need to be always checking those things from time to time.
2011 F-150 5.0L with tow package