Rotten egg smell
Does your hot water smell like rotten eggs? This is a subject that has come up a number of times in the RV Forum. Fortunately, the fix is relatively simple and virtually free. The following advice is offered by forum staff member Gary Brinck.
There's a bacteria that thrives in warm, dark, humid places and gives off a rotten egg smell (actually it's sulfur). It's not uncommon when a rig sits a while without being used.
The cure is to flush the tank a couple times. Also, super-chlorinate the system following this water system sanitizing procedure.
Regular flushing of the hot water tank will help prevent it from happening again.