Read my experience:
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27569419.cfm
Today's reply, probably the last of the thread.
What is in common with your question is I had experience with a 10 gallon water heater. They differ between brands.
The unit carrying the heater (coach, fifth wheeler, TT...) will vary the access to it.
I'd be surprised if your water line was actually welded to the tank, (access with an arc weld or lit torch?) but then there is still a lot to be learned about water heaters.