Exhaust Flue identification and clearances

My question is there are main types of flues out there from single wall to multi walled. Is there a stamp, label or a marking of some sort that I should be looking for that tells me what type of flue it is.

Further more what are the appropriate clearances for a single walled pipe compared to a multi walled pipe. Along with the clearance issue I have read in some posts that because fiberglass insulation is not flammable that it can be in contact with a flue but cellulose insulation can not. If someone knows of a good website with this information then please let me know. I have also attached some pictures that might present some more discussion.

I have also attached a picture of a water heater flue located in a garage that is missing a collar at the ceiling. I called it out because of the fire rating between the interior and exterior of the home. I just wanted to know if that how you would call that issue out or if it’s an issue at all.


For Canadians, some of these distances are different for different fuels. Refer to codes or manufacturer’s specs.

Great site David. Thanks!

All the B-vents I’ve ever seen have a label on them that specify 1" clearance. The site David posted says 2". All I’ve ever heard as an inspector is 1" for a B-vent and 6" for a single walled pipe. That company is located in the People’s Republic of California. Maybe that has something to do with it.

Here’s an example of what I say: “The water heater vent pipe is too close to combustible material, and should be serviced before the close of escrow. A single-walled vent pipe should be six inches away from any combustible material, and a double-walled vent pipe should be one inch away. This construction defect is considered a fire hazard. We recommend that repairs meeting the manufacturers specifications be conducted for fire safety reasons.”


Is the 6" for all fuels down there?

In Canada, it is:
-6" for gas
-9" for oil
-18" for wood

Joe F. is correct, Clearance to Combustibles: 1"


It appears that one of your INACHI brothers is using your name or was this really you???

NACHI Bashing, should… 11/1/08 10:46 AM Shut up you whining little bitch. You need a good bitch slapping. Love, Mario

Not me.

That’s the problem with this system, it doesn’t automatically show the member giving the rep.

It’s a very silly system if you ask me. It kind of reminds me of grade school, remember the stars the teacher gave students?

Brian, it appears that the rep system has become an obssesion with you. I suggest that you turn it off before you go into the red.

From my experiences with you, you surely use it more than any other member!!!

That’s because you are stupid!

OK, Mario!! You can have the last word. Now go take a few more pills!

I forgive you!:shock:

You obviously didn’t get the pills in you in time. Now you think you’re me…or has the obssession become so great you have 2 personalities (or more) inside your head…me and you!! When I’m not around you can still carry on the discourse…it’s just I can’t be there. Please record it!!

And get help!!!

Hey Boy,

You are one sick SOB, actually you are more like a cancer.
Go away and stay away!:roll:

Hey weirdo!! See you’ve been active in the tag dept also!! What!! No more reds to play with??

Listen here BOY, I get the last word here not you!!:roll::shock::wink: lol

Well, your last word(s) (the tags) show you’ve not evolved beyond a middle school mentality. Got any more words of wisdom???

Get a life boy!:wink: lol you crack me up!!