Probably one of the worst RV problems is having your blackwater tank develop stress cracks and leaking raw sewage... EPA nightmare
I was told by a number of RV repair shops that repairs were a waste of time and "just have it replaced"
Calling Four Winds (that owns Thor) I was told they didn't sell the tanks nor had any blue prints to help me figure out how to correctly remove it (I'm a full-timer & retired mechanic)
Cut to the chase... I filled tank with fresh water and drove it so tank would be cleaned out prior to removal and then spoke to another RVer that saw the stress cracks where it was slightly leaking and recommended a product called "Water Weld" by JB Weld as an option...
After cleaning & sanding the area thoroughly, I applied two packages to the entire collar and can personally say this product really does what it claims !
Added a piece of wood to support the "dump assembly" which probably contributed to the cracks.