View Full Version : B vent support

Robert Koch
05-16-2007, 05:32 PM
Additional strapping required? Having trouble confirming when support is required for double wall type b vent material (water heater vent) at/above roof. Scrolled through archives and read through G2424 (IRC) but cannot find reference.

Please advise. Thanks!


Robert Koch
05-16-2007, 05:36 PM
Here is the photo of the exterior vent above the roof.

Bob Harper
05-16-2007, 05:46 PM
Hi Bob,
This appears to be single walled vent connector and not B-vent. Regardless, the rules for B-vent would be found in the listed instructions. What I recommend is you take a photo of the listing sticker on a section of B-vent so you can later look up the mfrs instructions. The code instructs the installer to install to the listing, which is that booklet that comes with the B-vent. However, to get to the B-vent, you must use vent connectors, which are governed by the codes themselves.

In the pic shown, I would note the vent connector is tilted and needs to be plumb. They can use elbows higher up to offset it to line up with the vent. However, it should be properly supported so it doesn't wiggle around laterally and is supported vertically. There should be three screws per joint. The single walled pipe carries a 6" clearance to combustibles such as PVC pipe.

Do you have pics in the attic of the B-vent? The second pic appears to be a low roof pitch flashing as it is buckled up. Is this all B-vent and not single walled pipe? Generally, you can run up to 5 ft above the roof before you need bracing---as long as it is properly supported in the attic in 3 axis.

Is this a confined space?

How does that water shutoff isolate the WH?

I'd make sure those flex connectors are rated for hot water and not gas connectors. Can you provide a pic of the label?


Robert Koch
05-16-2007, 06:30 PM

Here is a photo of the vent from the attic. Clearance from insulation concerns. The vent (at the water heater) does change to double wall prior to the floor penetration. Additional clearance problems shown in the other photo. Yes, it is not secured at the water heater, neither is the draft diverter. Isolated shut off? No, it does not appear to be dedicated.

No photo of listing on the material.

Thanks again.


Bob Harper
05-16-2007, 11:19 PM
Wow! You need to notify them this is an extreme fire hazard! All that combustible cellulose insulation in direct contact with that vent is a recipe for fire. Must have an attic insulation shield.

Richard Stanley
05-17-2007, 08:10 AM
Is that asbestos insulation??

John Arnold
05-17-2007, 12:43 PM
As Bob mentioned - that appears to be cellulose insulation, not asbestos.

Robert Koch
05-17-2007, 04:40 PM
Thanks to all.