NG Water Heater - Venting question
I would like to relocate our natural gas hot water heater in our basement due to a proposed DIY replumbing project. The current vent is a single wall galvanized pipe that goes up through an old masonary chimney that used to be shared with a recently replaced gas furnace. This furnace was moved to a separate location in the basement and looks to vent via 3" PVC through a basement wall some 20 feet away. We'd like to remove the chimney to gain the space it occupies on the two floors above. This work I can do. But now we are scratching our head on how to vent this hot water heater and are wondering if we can accomplish this by relocating the water heater to be closer to a basement wall.
Mostly for financial reasons, I can't see us buying a power vent (I am assuming they are fairly expensive). So, we're looking to move this hot water heater and set up a new vent. I understand that I may need to use double-wall vent for clearance reasons if we go close to combustible material, but how do we run the vent now?
Can it just be run (with a slope greater than 1/4" per foot run) through an as-yet-unbuilt chase through the two floors above and then through the roof? Would it be easier to run it through the basement to an outside wall (10 feet away) and then up the side of the porch (porch on single level and therefore would not clear the peak of the 2nd floor roofline)?
I would love some ideas, examples, pictures, information sources, links.