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Discussion Starter · #1 ·
So on the house I purchased last year had a lot of renovations done by an incompetent's contractor (who is nowhere to be found).

The furnace in the crawlspace was replaced with a new 80% efficiency Goodman. The exhaust vent from the furnace connects to the transite oval wall pipe that goes up 1 floor into the attic, where it connects with old galvanized 6" pipe. Where this goes through the roof is where things go south, as it is clear they didn't know what they were doing and just screwed some random pieces together hoping for the best. Their install resulted in water leakage, as it appears they used a larger OD pipe to sleeve the exiting galvanize pipe, which lets condensation drip back on the inside of the sleeve.
See photos here:

Here is a video of the water leaking, which only occurs when the furnace is running, and happens regardless of snow on roof or rain. The amount of water increases as external temps drop:

I do not know what is actually happening between the "sleeve" and the top of the pipe on the roof, but I think there is not an actual connection and may be "open" for some distance, which allows the hot gas to condense and drip backwards.

I talked with a few HVAC contractors and their only solutions were to either run an entirely new flue, which would cost me closet or pantry space (which is in short supply) or to replace the furnace with a high efficiency and vent via PVC through wall in crawlspace. Not good or cheap options, I believe they were reluctant to mess with anything that had asbestos, which I understand.

What I want to do is replace all the vent piping starting at the top of the oval wall pipe, and then use 1 or 2 pieces of B vent to go up through the roof and properly flash. Can I just use something like this to connect to the old transite wall pipe: Amerivent 4" Oval/Round Adapter B-Vent | HD Supply

TLDR:

I want to replace all the vent piping starting at the top of the wall pipe, and then use 1 or 2 pieces of B vent to go up through the roof and properly flash. Can I just use something like this to connect to the old transite wall pipe: Amerivent 4" Oval/Round Adapter B-Vent | HD Supply
 

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That water may be from the exhaust cap area. Might want to check on the roof if the used a storm collar. If they didn't, then that is why your getting that water.

That looks like a regular roof jack set up.

The flue pipe in the crawlspace sow not be single wall. It should be Bvent. The Transite is also too large for the furnace. They should have dropped Bvent down through it, then the furnace Bvent pipe connected to that Bvent pipe.
 

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Discussion Starter · #3 ·
That water may be from the exhaust cap area. Might want to check on the roof if the used a storm collar. If they didn't, then that is why your getting that water.

That looks like a regular roof jack set up.

The flue pipe in the crawlspace sow not be single wall. It should be Bvent. The Transite is also too large for the furnace. They should have dropped Bvent down through it, then the furnace Bvent pipe connected to that Bvent pipe.
Thank you for the helpful insights!

With regards to the water coming from the "exhaust cap area", and the storm collar, wouldn't that only cause water to flow down during rain or snow melt? Water is produced regardless of rain or snow on the roof.

I do not believe that the portion of the flue that goes through the roof and up is "standard". You can see where they used screws to secure the "sleeve" to the old single wall pipe. In the photo of the roof you can also see that there are two B vent pipes, one inside the other. I'm not sure why this is, or what is going on under the flashing, but I think that whatever is happening is not continuous. I think they couldn't find a way to connect the old signle wall pipe to B vent, so rather than replacing they just slapped a sleeve on to connect things.

photos of screws and "sleeve":


Photo of exhaust cap and roof:

I suppose regardless it does not matter if the flue pipe is too large. So based on what you are saying, what I should do is remove the piping that exits the wall pipe, and place this inside the existing wall pipe?:


Then I can connect at the bottom and top running regular B vent?
Thanks again!
 

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The outer sleeve is to provide the clearance to combustibles that code requires. But it looks like it isn't even 1" of clearance.

I would run all new properly sized Bvent.

Over sized chimney/Bvent causes the combusted gas to cool and condense in the chimney/flue.

If the transite is big enough inside. The Bvent can be ran up through it.
 

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Discussion Starter · #5 ·
The outer sleeve is to provide the clearance to combustibles that code requires. But it looks like it isn't even 1" of clearance.

I would run all new properly sized Bvent.

Over sized chimney/Bvent causes the combusted gas to cool and condense in the chimney/flue.

If the transite is big enough inside. The Bvent can be ran up through it.
Thank you!

If the Bvent does fit within the transite pipe, I assume I will have to cut the bottom of the transite in order to connect the next piece of B vent.

So I would need the proper lengths of this:

Then either of these on the bottom:


I ask because I want to make sure this is the best plan, and there isn't a plan that would allow me to avoid cutting the bottom off of the transite pipe.

If it does need to be cut, and I use one of the pieces above (Tee or oval to round adapter), what would be the best way to support the weight of the newly installed vent piping?
 

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In the crawl, blocks to support it. And then a holding plate where it penetrates the old roof..
 
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