I got the water heater working, it's supplying me with hot water again.
Last night I got a little more accomplished on the dust collector. Mostly what I got done was discovering that I am in dire need of 1/8"x1/8" pop rivets for the sheet matal to sheet metal joints, I only had about 5-6. I'm also in need of the sheet metal screws for the sheet metal to plastic joints. I will take care of those defficiencies on the way home tonight. Last night I also printed out a 4" flange and there's another on the printer now. So I'll either have a finished flange waiting for me when I get home - or a mess if the printer screwed up. Those flanges will allow me to take apart the duct-work when needed - without having to resort to a sawzall.