Underbelly wet!!!!

I have a 2015 178. I discovered I had a wet underbelly when installing back up lights at rear of trailer. Probably the last 6-8 inches of the bottom of the floor. First thing I did was move the trailer inside and start a drying process, I didn't remove anything. Secondly I sealed the spoiler with eternabond tape. I kept the trailer out of the weather all the winter months. I moved it outside, and monitored the floor are for wet, near all the water sources, it stayed dry. One thing I noticed was the protective black undercoating holds water in, there is no way for water to drain from the floor. The floor is dry, so it appears the spoiler was culprit in my case. I could test it with an awl and find wet areas. Once I penatrated the black covering, if it was wet I'd get a drop of water. For me it was a matter of getting it dry and then trying to figure out what would make it wet. I wasn't ready to just quit and get rid of the camper until I tried to fix it.

For me, it was easier to see if floor was wet with ice pick or awl versus remove the coating. Since I dried I have replaced some undercoating. Weird as it sounds, I was trying to figure how water would get from top to bottom without wetness on inside or top of floor. That's when I went to spoiler leak. In my case only the bottom was wet, the inside was dry and stable.

Following .... I have a prior post on wet floor that is sagging on a 2014 182g, along the side with the slide out.  (from the slide side to the rear of the trailer has dropped 1-2 ") Good luck with your repair.

For the 178, I would suggest you remove the mattress, just fold it in half and muscle it over to the table side. Remove the screws from the plywood decking under the mattress and check all the water connections that are under it next to the heater. I found a leak on the inside for the city water hook up. Even if you never use the city hook up there is water pressure on the inside whenever the pump is on, and when you’re traveling with any water in the tank it can leak out of those water fittings.

I will check that today too, thank you!