View Full Version : Chiney Liner Galvanized Pipe

Carl Salamone
10-02-2010, 07:18 AM
I have an "exterior" masonry chimney with 7" x 7" clay tiles. I need to add a liner for a combination Category I gas furnace and WH. I talked to a local guy who said that I could use single wall galvanized vent pipe. I also considered putting type B vent in there - thinking that the type B would provide some insulation for my cold climate here in WI.

I like the rigid pipe over a flex liner because the clay tiles are loose and the rigid pipe has less risk of a pinched liner in the event that the stack tumbles. The SSteel rigid is horribly expensive and from what I'm hearing locally, would be way overkill.

Any thoughts? Thanks.


Michael Thomas
10-02-2010, 09:21 AM


Carl Salamone
10-02-2010, 09:29 AM
Thanks Michael, I see that single wall is a bad idea for two reasons: 1) Not allowed in cold climate, and 2) Not allowed in concealed space.

Anyone see any issues with using type B inside the chimney / clay tiles?



Michael Thomas
10-02-2010, 09:53 AM
I like the rigid pipe over a flex liner because the clay tiles are loose and the rigid pipe has less risk of a pinched liner in the event that the stack tumbles...

Sounds like the chimney itself might be a cause for... um... "concern"?

Carl Salamone
10-02-2010, 10:19 AM
Well... Its a freestanding stack of clay flue liner tiles. Its not supported by the concrete block wall in any way. From what I've been told, that's how they used to do it here in WI (circa 1976). A rigid liner should give it the stability required to prevent a liner tile collapse. ...which is why I'm steering away from the flexible liners.

Bob Harper
10-02-2010, 03:48 PM
No, you cannot use galvanized steel pipe as a chimney liner under any circumstances. The code states all liners must be listed and single walled galvy is not. It is 'connector'---not 'liner'.

You could use B-vent if it is approved for use as a liner by the mfr. as several are. However, I discourage the practice for several reasons: the joints can disconnected and you cannot see it. The outer galvanized steel will rust out unseen. It carries a 25 yr warranty at best and some are only a year or two.

If you are worried about a liner crushing from a dislodged flue tile, you must be referring to cheap aluminum liner. Even most cheap stainless liners will not collapse from flue tiles falling against them but alum. certainly will. Aluminum will also crush, rip, come apart and deform during installation. In Wisconsin, I would expect about 3 yrs at most out of an alum. liner. Do yourself a favor and get the 'obscenely expensive' stainless steel liner with the transferrable lifetime warranty. The top brands won't crush--you can stand on them. You have to worry about joint integrity with rigid liner, which includes the stainless steel pop rivets. At least flex stainless will last and you will waked up the next morning. If your chimney is inherently unstable, tear it down and rebuild it. You don't rely on liners to stabilize chimneys. If the furnace is a fan assisted 80%er, have a post purge timer installed, remove the draft hood on the wh and replace it with a double acting barometric damper with spill switches to both the furnace and WH ,then perform combustion analysis and get yourself a low level CO monitor----------and a new chimney consultant because the one advising you obviously does not own a code book.