Replacing Water Heater Vent Pipe

[oldnewhouse]

Hi all,
I'm nearing the final stages of finishing our basement and I'm now stuck on the gas water heater. Currently the vent pipe is single wall and runs for about 6 feet from the water heater to the hole for the vent through the chimney. It cuts through a wall that's just got a big hole in it now - leaving plenty of clearance for the hot single wall pipe. I'd like to finish things off and close in the pipe. A double wall vent pipe setup seems to be 4" too long (two 3' pieces and 2 elbows). I'm told that I shouldn't close in the single wall even if nothing is touching it (I'd make a soffit). Is there a good way to cut the double wall pipe and still have it fit together nicely? Is it ok to just enclose the single wall if I give it room to breathe and keep wood off of it?
thanks
Mark

[DUNBAR PLUMBER]

You can erase that 4" by going single wall right at the water heater, but when you start to close the pipe in, switch it two double wall B vent before it gets closed in.


So, single wall 90, short piece of single wall pipe, thimbled into double wall to make it work out. I would say there's no way you're closing that water heater in extremely close to the unit itself. That would make it horrible for replacement in the future.

[mikes334]

I would look into getting a smooth wall chimney liner (http://www.chimneylinerdepot.ca/store/). It will help in creosote build.