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Leak around previous furnace exhaust vent in basement

  • Last Updated:
  • Apr 5th, 2020 11:48 pm
[OP]
Sr. Member
Aug 30, 2013
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Leak around previous furnace exhaust vent in basement

I noticed a small drip around my old furnace vent later in the summer 2019 in my basement. It seemed to be dripping from the outside of the vent pipe. just along one side. Nothing crazy, a bucket underneath captured whatever fell. Maybe 1/2 in my bucket. Nothing much. Wasn't a a big deal. It didn't leak every rain.

This spring Lots of melt lately but nothing additional in terms of drip, but continued small leak along outside of vent pipe. Rained heavy early this week, but nothing more then the same leak.

Snowed a lot later in the week, and today's melt I'm noticing the leak is on the other side now also. But it's not dripping at the end of the vent on the other side, from where I can see. I have a cut in the plywood just a couple inches away and see a drip coming through there. The wood along 2.5 sides of the vent are wet.

In the pic where it's red marked, is wet. The 2 red circles are the spots where water is dripping. The blue is where it's dry and not wet.

Think there is some roof work that needs to be done around the old vent? Maybe some cracking of the sealant or bad shingles?

We went up to the roof to take a peak in the fall, but didn't see evidence of anything wrong (mind you I'm a first time homeowner).

Any suggestions on how to proceed and what it likely is?
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14 replies
Deal Fanatic
Jan 25, 2007
9943 posts
5234 upvotes
Paris
Water is getting into the chimney cap. I think your issue is likely that.

Actually, is the outside of the pipe wet? If so, its leaking at the roof. If its inside the double walled pipe, its the cap.
Sr. Member
Oct 22, 2016
660 posts
563 upvotes
Comox Valley
First thing I would check is the caulking around the B-Vent collar, as photo, and where his hand is at. It is a common enough to happen fairly regularly.

At times this caulking will wear away, causing the leak you describe. I suggest you caulk it, and at that time, inspect vent on roof, and roofing materials around it.

Note, of photo, I took it off the web. It is not my own caulking job Smiling Face With Smiling Eyes
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Deal Fanatic
User avatar
Dec 28, 2007
7957 posts
4578 upvotes
Alberta
User452441 wrote: First thing I would check is the caulking around the B-Vent collar, as photo, and where his hand is at. It is a common enough to happen fairly regularly.

At times this caulking will wear away, causing the leak you describe. I suggest you caulk it, and at that time, inspect vent on roof, and roofing materials around it.

Note, of photo, I took it off the web. It is not my own caulking job Smiling Face With Smiling Eyes
Had the same leak in mine a couple of years ago. As in the picture, this was the exact spot where the caulking separated. Re-sealed it and stopped the leak. So far so good.
[OP]
Sr. Member
Aug 30, 2013
735 posts
761 upvotes
prairies
Jerico wrote: Water is getting into the chimney cap. I think your issue is likely that.

Actually, is the outside of the pipe wet? If so, its leaking at the roof. If its inside the double walled pipe, its the cap.
this inside of the vent is completely dry. i removed the cap that was inside at the bottom and there was just dry dirt in there. so its not wet inside the vent duct.
Deal Fanatic
Jan 25, 2007
9943 posts
5234 upvotes
Paris
marcfar wrote: this inside of the vent is completely dry. i removed the cap that was inside at the bottom and there was just dry dirt in there. so its not wet inside the vent duct.
It’s double walled so there are 2 pipes. Is the exterior of the outer pipe wet?
[OP]
Sr. Member
Aug 30, 2013
735 posts
761 upvotes
prairies
Would meting snow actually get through the b-vent collar even if there is not snow built up to the collar. I dont think the snow is that high up to reach the collar, and its more along the surface where the shingles would be. but ill go have a look when I can borrow a ladder.
As per your photo, is I see a little bit of caulking around the duct along the roof shingles, could that be a spot I could re-caulk also?
Last edited by marcfar on Apr 5th, 2020 7:39 pm, edited 1 time in total.
[OP]
Sr. Member
Aug 30, 2013
735 posts
761 upvotes
prairies
Jerico wrote: It’s double walled so there are 2 pipes. Is the exterior of the outer pipe wet?
Yes.
Deal Fanatic
Jan 25, 2007
9943 posts
5234 upvotes
Paris
marcfar wrote: Yes.
So its likely the boot on the roof. Easy enough fix, just somehow get some good caulking. Tougher in Ontario with all hardware stores closed.
[OP]
Sr. Member
Aug 30, 2013
735 posts
761 upvotes
prairies
Jerico wrote: So its likely the boot on the roof. Easy enough fix, just somehow get some good caulking. Tougher in Ontario with all hardware stores closed.
Im in MB, so I think hardware stores are still open.
Sr. Member
Oct 22, 2016
660 posts
563 upvotes
Comox Valley
marcfar wrote: As per your photo, is I see a little bit of caulking around the duct along the roof shingles, could that be a spot I could re-caulk also?
Could be, it is possible to separate at the joint. The best ones when they are manufactured are soldered, but others ones, are caulked at this joint.
[OP]
Sr. Member
Aug 30, 2013
735 posts
761 upvotes
prairies
User452441 wrote: Could be, it is possible to separate at the joint. The best ones when they are manufactured are soldered, but others ones, are caulked at this joint.
t
I was looking at the boot piece online, as mentioned by other poster. hey all seem to be 1 piece silicone or rubber looking now at homedepot. I wonder if that will help prevent any leaks as there wont be any caulking to place around the base by the exhaust pipe along the roof.
Deal Fanatic
Jan 25, 2007
9943 posts
5234 upvotes
Paris
marcfar wrote: t
I was looking at the boot piece online, as mentioned by other poster. hey all seem to be 1 piece silicone or rubber looking now at homedepot. I wonder if that will help prevent any leaks as there wont be any caulking to place around the base by the exhaust pipe along the roof.
When I did mine in Ontario for my garage heater, everything was required to be metal... no rubber. The point of double walled b-vent is that it dissipates heat so it doesn’t burn rubber and wood things.
Sr. Member
Oct 22, 2016
660 posts
563 upvotes
Comox Valley
marcfar wrote: t
I was looking at the boot piece online, as mentioned by other poster. hey all seem to be 1 piece silicone or rubber looking now at homedepot. I wonder if that will help prevent any leaks as there wont be any caulking to place around the base by the exhaust pipe along the roof.
I would take it that you are not allowed a one piece silicone, or rubber, because it is for your mid efficiency furnace, where a b-vent is mandated.

If your furnace is a high efficiency furnace, plastic vent pipes can be used, then you can use rubber.

Feel free to correct me, if I am wrong.
Deal Fanatic
Jan 25, 2007
9943 posts
5234 upvotes
Paris
User452441 wrote: I would take it that you are not allowed a one piece silicone, or rubber, because it is for your mid efficiency furnace, where a b-vent is mandated.

If your furnace is a high efficiency furnace, plastic vent pipes can be used, then you can use rubber.

Feel free to correct me, if I am wrong.
This is his old b-vent which was capped inside

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