Any water lines in the walls or floors adjacent to the wet spot?
I know you are on a permanent site, but I would probably turn off the city water, fill the fresh tank and run on the pump for awhile. If the pump comes on periodically w/o opening a faucet, you might have a leak somewhere.
Or just turn off the water next time you leave and see if that wet spot dries out.
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder