Vent Pipe Manifold

RobertM · May 31, 2010

My furnace and water heater are both gas-fired. They feed into this single wall galvanized removable section with inlets for both. The riser appears to be double walled. It is of '50s vintage and not "Type B", which I believe might be required, as the furnace was installed 2 years ago and the installer used Type B duct to connect to this. I'm guessing there are sections with 6" and 3" inlets that can be connected up, as well as an endcap to make up another comparable fitting. Is this the way to go or are there alternatives? Where can I find this stuff locally, HVAC shop or Plumbing supply? It would actually be more convenient to have an on-line source.

hj · May 31, 2010

I am not even sure WHAT the problem is, or if you even have one. Whatever you get will normally be proprietary and not interchangeable with other brands, so if you order from the Internet and come up short on some pieces, you will probably NOT be able to buy those sections locally.

Sponsor · 2022-01-29T12:20:58-0800

RobertM · May 31, 2010

Sorry, forgot to post photo. Actually, it is a Type B vent from the furnace to this single wall manifold that also takes in the water heater vent. Riser pipe is double wall up to the roof. I'm calling the lower piece a "manifold", as two vents go into it. The heater (39,000BTU, 40 gallon) vent is currently single wall also. Because the contractor installed a Type B, I'm guessing it needs to be "B" all the way. This manifold is also showing some age and could rust through within 10 years, so it is in need of replacing. Does it need to be double walled? Does my water heater vent too?

hj · Jun 1, 2010

Single wall is perfectly adequate, as long as it is NOT within 6" of a combustible material. Is that "manifold" sitting on top of a piece of wood for support? Type "B" needs 1" of clearance.

RobertM · Jun 1, 2010

It is about 1" from wood. It has another problem in that there are gaps where the fittings attach to the main pipe. A bit of rust on the inside. A single wall unit looks easy to build (well, at least easier).

hj · Jun 2, 2010

Aluminum tape will seal the gaps, and a "class B" vent would be VERY difficult to construct unless you had a lot more space than you do there.

Doherty Plumbing · Jun 2, 2010

On the contrary actually. B-Vent comes in pre-fabbed lengths and simply just locks togeather where as C-vent needs to be cut and put togeather.

The gap around the joints aren't a problem (as long as they're not noticiably big) because they'll simply just draw in a bit of extra dillution air as the flue gases rise.

As for your original question you could simply just pull the old vent out and drop in a new with current b-vent. Ofcourse you should pull a permit and have it inspected but it's not rocket science to do it.

hj · Jun 3, 2010

He HAS a "B" vent, he is asking about the single wall component where the two connections are made. Doing THAT with "B" vent would require TWO tees and he does NOT have enough height to install them.

Shacko · Jun 3, 2010

Just make sure you add a carbon monoxide detector when you're done!!

Doherty Plumbing · Jun 3, 2010

hj said:
He HAS a "B" vent, he is asking about the single wall component where the two connections are made. Doing THAT with "B" vent would require TWO tees and he does NOT have enough height to install them.

Well he would if he installed a new b-vent chimney going up because he could shorten it up and raise the T's closer to the ceiling. This just may give him enough room.

Assuming he wants it all in B-vent.

hj · Jun 4, 2010

And WHY would he want it unless there was a fire clearance problem. And even then there are less costly methods to avoid them.

Doherty Plumbing · Jun 4, 2010

Ask him not met

Vent Pipe Manifold

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