Heady, I am definitely going to look around some more, but my first inspection found nothing. I also had the same thoughts as clubhouse regarding expansion and contraction since we had highs in the mid 70's and lows in the low 40's at night.
Regarding the roof, I have inspected it even though it is a new camper. Didn't see anything out of the ordinary. I also had it sitting out during another rain before I sold my old camper and never spotted a leak. Another reason I am thinking it was a bonehead mistake on my part.
eldermike, I use to do the same thing with my old camper. It was a 1972 that I refurbished. Not sure why I didn't do the same with this one. Guess just a little over confident being that it is new. I think I will go back to turning the water off whenever we are away and at night from here on out.
clubhouse, sorry for the issue, but I am kind of glad that I am not alone in chasing this gremlin.
And as mentioned, I had the same thoughts on expansion/contraction.
Roy, as stated in my post, we did not have water hook up (I haven't grasped the "city water" term...kinda hard to do so when we are nestled back in the National Forest camping) we did have electric hook up. When I do have water hook up, my pump is off.
Thanks for the replies. If I find anything I will report back.