Originally Posted by coderguy
What if I switched over to a tankless water heater?
With tankless you'll most likely have to up-size your gas line, maybe even your whole gas system and meter. There are power vented water heaters like ben's plumbing said, and there are also water heaters that are just like regular water heaters, but instead of power venters, they use a concentric vent that can go out the side wall, just like a fireplace. I've installed a few, but I don't recall who made them. A little googling may turn something up if I don't remember the name.
Edit: found a link to the manual: http://www.bradfordwhite.com/images/...als/45839C.pdf