Leaking furnace exhaust

[earl84]

I have a small leak from furnace intake/exhaust. I did not know until yesterday that the exhaust and intake shared the same roof penetration. This is over the garage and it is a very small leak, was hoping to find the exact spot but access is limited. I suspect that snow has gotten up under the storm collar (We've had a lot of snow this year) and melted. It's a little tricky due to it being right on a rib of the metal roof, compounded by the fact that I don't like getting up there since it's sort of slick. But you gotta do what you gotta do.

Anyone have any suggestions on how to proceed?

 

[LiketoFix]

Intake and exhaust are supposed to be separated as per that reason. Fumes, Safety.
If there's any way to separate those two for Safety sake wouldn't be a Bad Idea. I know it probably adds more work to what the solution is to your problem and the answer that your looking for but Carbon Monoxide gasses and fumes are no Joke!!!
Any short term goop or fix might be the Easiest but not necessarily the Best!!! IMO!
LtF

 

[PCustoms]

Intake and exhaust are supposed to be separated as per that reason. Fumes, Safety.
If there's any way to separate those two for Safety sake wouldn't be a Bad Idea. I know it probably adds more work to what the solution is to your problem and the answer that your looking for but Carbon Monoxide gasses and fumes are no Joke!!!
Any short term goop or fix might be the Easiest but not necessarily the Best!!! IMO!
LtF

Not if it's a factory concentric vent....

@earl84 who installed that?

I sure hope it's not just a wye, but the roof penetration is definitely wrong. There should be flashing that matches the rib profile and goes over the downhill side of the panels. That mess you have is just destined to leak.

 

[earl84]

Well, I’m no HVAC guy, but I think these two are strictly for the burner side of this NG furnace, and separated from the air that makes it into my house.

 

[earl84]

Not if it's a factory concentric vent....

@earl84 who installed that?

I sure hope it's not just a wye, but the roof penetration is definitely wrong. There should be flashing that matches the rib profile and goes over the downhill side of the panels. That mess you have is just destined to leak.

It was that way when I bought the house, and after looking online yesterday, I pretty much suspected it was installed poorly. I’m thinking I need to cut the whole mess off at an appropriate height above the roof, install new flashing, coupler, add pipe back to proper height, and a new vent cap.
https://abrwholesalers.com/cventcap4-div-outside-cap-assembly99072. I found this yesterday, too, all this is new to me.

It loops like a factory concentric vent, when I looked at it with binoculars, it was embossed with “Do not block intake.”

 

[PCustoms]

It was that way when I bought the house, and after looking online yesterday, I pretty much suspected it was installed poorly. I’m thinking I need to cut the whole mess off at an appropriate height above the roof, install new flashing, coupler, add pipe back to proper height, and a new vent cap.
https://abrwholesalers.com/cventcap4-div-outside-cap-assembly99072. I found this yesterday, too, all this is new to me.

First thing you have to do is determine if it's a proper concentric vent or just a PVC hack job. If it's a concentric vent you need to find a boot that fits the vent and be careful not to cut the vent itself.

If it's a Cobb job using a PVC y fitting, then you'll have to see if you can source the correct concentric vent, or separate the pipes and do two roof penetrations.

It seems like most of the factory roof penetration boots I see sit on top of the metal r panels, my preference on the few that I've dealt with have always been to tuck it under the uphill side and over the downhill side of the roof panel, that way it naturally sheds water and does not rely on sealant.

 

[Fav Onefour]

It looks like a proper concentric. In fact, the HVAC portion is probably done correct if it has spec height. I'm guessing a quick roofing job was done later on and they just cut around the whole works.
I wonder if it has the removable style cap? That would save quite a bit of hassle.
For the flashing, you have a couple of options. Drop a new flashing over the top and hope. Or, peel back the steel and redo it completely with proper overlay.
Caulk gun repairs usually mean you are planning on going back up there again.

 

[PoorUB]

That definitely is a concentric vent, nothing wrong there!

Just figure out where the roof penetration is leaking and fix it.

 

[earl84]

I think it’s all correct, the furnace has worked flawlessly for 4 winters now. I’ll figure the lathe forward and fix it in the next month or so. Too cold right now, and the leak is minimal. It’s not as cold as PoorUB’s neck of the woods. I grew up in Casselton, 20 miles west of FArgo.

 

[Bert_]

Whoever did the caulk job shouldn't be anywhere near a roof but unfortunately you see that kind of thing a lot.

That said penetrations through tin roofs are a pain. The common rubber boots that everyone uses are ok but they still rely on caulk to seal. I did a flashing on my garage with a regular metal flashing and ordered one panel longer than the rest so I could have a seam to layer the flashing into. I expect it will outlast the roof.

 

[Bert_]

That furnace could likely vent out a side wall if it's not too difficult. It looks like you have an old piece of b vent with PVC ran through it.

 

[Jim greengo]

Intake and exhaust are supposed to be separated as per that reason. Fumes, Safety.
If there's any way to separate those two for Safety sake wouldn't be a Bad Idea. I know it probably adds more work to what the solution is to your problem and the answer that your looking for but Carbon Monoxide gasses and fumes are no Joke!!!
Any short term goop or fix might be the Easiest but not necessarily the Best!!! IMO!
LtF

Probably a concentric kit,spell check.

 

[PoorUB]

Whoever did the caulk job shouldn't be anywhere near a roof but unfortunately you see that kind of thing a lot.

That said penetrations through tin roofs are a pain. The common rubber boots that everyone uses are ok but they still rely on caulk to seal. I did a flashing on my garage with a regular metal flashing and ordered one panel longer than the rest so I could have a seam to layer the flashing into. I expect it will outlast the roof.

When you stick a pipe up through an existing roof you gotta do what you gotta do, but I agree, that penetration is all kinds of screwed up!

We used boots like this all the time on metal roofs.

https://www.flashingsdirect.com/2-r...lY8xios-CG1bJvrcosFPGH-2j69v4e54aAkmVEALw_wcB

This boot and a tube of Sikaflex LM and it will not leak.

I see guys use silicone and IMO, silicone is crappy sealant compared to Sikaflex. I will not use silicone, period. You won't find a tube of it in my property other than the small tubes for engine work and even then I don't use much.

 

[b-boy]

That furnace could likely vent out a side wall if it's not too difficult. It looks like you have an old piece of b vent with PVC ran through it.

Yup - Through a wall. This is what I did. I have a concentric setup that vents through the closest wall. It vents about 12 ft up, and has to stick out a little past the roof overhang.

I did not want to put any holes in my roof.

 

[larry4406]

I did not read all of the prior posts.

That appears to be a PVC concentric kit. It will use a normal 4" plumbers roof boot not the **** you have.

 

[earl84]

When you stick a pipe up through an existing roof you gotta do what you gotta do, but I agree, that penetration is all kinds of screwed up!

We used boots like this all the time on metal roofs.

https://www.flashingsdirect.com/2-retrofit-pipe-flashing/?keyword_session_id=vt~adwords|kt~|mt~|ta~&_vsrefdom=wordstream&gclid=Cj0KCQjwt_qgBhDFARIsABcDjOdoRBRa2ypmPDZOZNye-NIlY8xios-CG1bJvrcosFPGH-2j69v4e54aAkmVEALw_wcB

This boot and a tube of Sikaflex LM and it will not leak.

I see guys use silicone and IMO, silicone is crappy sealant compared to Sikaflex. I will not use silicone, period. You won't find a tube of it in my property other than the small tubes for engine work and even then I don't use much.

I think this might be the easiest route. Thanks for that link. Looks like I might have to cut off that lower galvanized boot below the storm collar to make it work. Anyone see a problem with that? I’m starting to hate silicone as well. Sikaflex is a lot cheaper than having to do this repair again.

I want to thank everyone for their input, it’s really appreciated.

 

[PoorUB]

I think this might be the easiest route. Thanks for that link. Looks like I might have to cut off that lower galvanized boot below the storm collar to make it work. Anyone see a problem with that? I’m starting to hate silicone as well. Sikaflex is a lot cheaper than having to do this repair again.

I want to thank everyone for their input, it’s really appreciated.

You buy a rubber boot that fits around the PVC concentric and get rid of the galvanized boot completely. I also mentioned Sikaflex LM. If you use silicone you will be back repairing it in a couple years. The proper sealant is a great part of it. Also that rubber boot can be formed to match the contour of the ribs in the sheet metal. Then you caulk under it, screw it down with a bunch of #8 sheet metal screws, maybe one every inch. The caulk well around the edges and caulk over all the screws.
If you can not find Sikaflex LM at a home center, try look for construction supply house, one that serves professional contractors.

 

[gmcgeo]

You need the proper size master flash boot for this.

Get rid of what you have, it will always leak.

 

[danski0224]

I have a small leak from furnace intake/exhaust. I did not know until yesterday that the exhaust and intake shared the same roof penetration. This is over the garage and it is a very small leak, was hoping to find the exact spot but access is limited. I suspect that snow has gotten up under the storm collar (We've had a lot of snow this year) and melted. It's a little tricky due to it being right on a rib of the metal roof, compounded by the fact that I don't like getting up there since it's sort of slick. But you gotta do what you gotta do.

Anyone have any suggestions on how to proceed?

That's a ****** install.

Maybe someone here on GJ was looking for info on how to DIY a metal roof penetration and flashing?

When the roof was done, that should have been moved over to the "flat" part of the panel.

Anything "on top" of the roof panel will always rely on some sort of caulking or sealant to do the job.

You could look up the roof panel manufacturer recommendations for flashing and detailing roof penetrations. I would start there.

Caulk and paint make you the tinner you aint.

 

[weadjust]

I did a flashing on my garage with a regular metal flashing and ordered one panel longer than the rest so I could have a seam to layer the flashing into. I expect it will outlast the roof.

The rubber boot around the pipe will dry rot and need to be replace a few times during the life of the metal roof

 

[earl84]

The rubber boot around the pipe will dry rot and need to be replace a few times during the life of the metal roof

Youre probably right, but I ordered the boot that PoorUB showed and it arrived yesterday, along with the Sikaflex. That's the route I'm going to take for now. Thanks, GJ.

 

[PoorUB]

Youre probably right, but I ordered the boot that PoorUB showed and it arrived yesterday, along with the Sikaflex. That's the route I'm going to take for now. Thanks, GJ.

Those boots will last for years. Yes it will need to be replaced at some point, maybe 10-15 years from now!
When you fit that boot work the base over the ribs, get it bent around so it follows the contures. Run a heavey bead of Sikaflex under the boot where you screw it to the roof panel, then follow up with a bead all around the edge of the boot blended in with your finger. Run another light bead where the boot meets the pipe and blend it in with your finger.

Just a warning. After Sikaflex dries, nothing will clean it off. If you get it on your hands it is pretty much there to stay! If you hit it before it sets up, brake cleaner does well to remove it. I would carry a can on the roof and a hand full of towels. You can try latex gloves, but they need to be heavy thick ones as the Sikaflex is thick and sticky. It will try remove or tear a cheap latex glove.

I always applied it bare hands and cleaned up ASAP.

The only thing I have found to clean it off later is GoJoe and a scotchbrite and wear it off!