I double welded the firbox chamber.Then I welded the tank inside and out on all sides except for the last panel i put on.I could only weld it from the outside.After all the seams and ports were welded.I then welded a cap over the water level pipe that exits the top of the tank,installed the ball valves for the water ports.I then presurrised the water cavity.MAX OF 10PSI ONLY!!!! I used around 8 psi mostly to check the leaks.I used glass cleaner in a spray bottle as it bubble up quicker than dish soap did..
I then sprayed all the seams inside the firbox,and then on the outside of the tank.
When you find a leak,mark the spot with something,Then dump the air out,then go back and do the weld repair.Then represurise the tank and re check for leaks.
This is a time consuming process but it is what has to be done.
You don't presurise the burn chamber.just check it on the inside when the whole thing is assembled.