Leaking furnace pipe

What can I try to stop a small leak between the pipe and the wall flashing? I’ve already used hitemp silicone on the storm cap.

I would try cutting out shingles to form a channel around the boot so the water has a place to go, but the flashing and shingles go right under the wall flashing.

Thanks for lookin’

Tear that area apart, replace pipe flashing and cut it in properly. Maybe just the picture but this roof looks way too flat for shingles. If you keep caulking things you’ll chase this leak for years.


What size boot for a pipe thats 24" circumference, about 7.5" dia ? The one’s Home Depot sells are for B Vent, mine looks like a single wall.

Talk to a HVAC supplier.


You can get a tapered flange from HVAC supplier and trim for an exact fit. You will also want a weather ring/ storm collar for above the flange. I would get the largest one possible and or solder an extension to the right side so it is long enough to bend it 3" up the wall. Then install it as one big step flashing.


I’m having a hard time understanding what you mean, is there some visual depiction I could see? Surely I’m not the only one who has had to put a boot right up against a wall.


What MPA is describing is really the best way to handle the issue. However, its not really a diy job.

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I think The leak is more likely at the wall.
The water is running under the flashing.
The flashing is supposed to be under the shingles.

Re-seal where the sealant has wore away
Where the flashing meets the shingles
The top of that flashing too(wall side)
And you might solve the issue.

It really needs to be torn out and done right.
But that might solve it for a while.