I need to extend my auger tube. What size pipe? The auger fits inside a 2" pipe but it is too small on the outside to fit snuggly in the collar on the burner. I made a custom jacket for the outside of the boiler and I only have double bubble insulation on it so far. What a difference it has made allready. I am putting 3" of blue board on top of the double buble. It will be tight as a drum.