It depends where the crack is.
Mine was cracked in the tank. I couldn't consider epoxy because the tank would flex at the crack as the air pressure increased.
I was lucky that the crack was accessible simply by removing the side cover grill. I hired a welder that specialized in aluminum welding. He welded it, added reinforcement to the tank to prevent it cracking again, and pressure tested it.
That was two years ago, and it's been fine ever since.
2016 Creekside 23RKS
2012 Ram 2500 Laramie 4X4 Cummins 6.7L