I have a Trillium
4500 as well. We've fixed various leaks
. Some have required hose testing, etc. A few months ago we fixed a leak in the rear left corner in which water water accumulating under the cushion, similar to your leak. In our case the water was coming in through the belly band fasteners.
The problem with belly band fastener leaks
is that the water tends to travel around the band. We did a temporary but very effective fix: We removed the vinyl insert, cleaned and sealed (with a quality exterior sealant) all fastener heads, re-installed the vinyl insert, AND also applied sealant between the top edge of the metal band and the upper body of the camper. We did this ALL the way around the camper. We no longer have belly band leaks
- The permanent belly band fix, as documented in other threads, is to remove the belly band, remove rusted fastening plates behind the belly band, repair and reinforce the fiberglass.
- Another prime source of leaks is the window frames, so that is another possibility. The fix is to remove, re-seal and re-install the windows
. Again this is extensively documented on other threads.
Appears you have an otherwise wonderful camper!