RE: Lesson Learned From Silicone Caulk--ROOF FLANGE??

[Giles]

While on the roof and I have something I have never seen. The 3 inch PVC pipe that extends out roof, is inside an all metal roof flange. I understand the purpose but don't think it was installed properly. It appears that the waterproofing between the PVC pipe and the Metal Flange is accomplished by bending the top edge of the metal pipe down inside the PVC pipe.
It appears to have been POUNDED in place, with the PVC pipe being app 2" below top surface of metal flange!
The metal appears to be soft and I assume it is a Lead alloy??????
Other then the small leak, I believe the 3" PVC is essentually a 2" because of the sloppy installation of the wrinkeled up metal.
Is this something I should be concerned about--I am having NO Vent problems?

 

[Hunderliggur]

A pic would be useful, and this does not sound correct. 2" or 3" effective vent is probably not a problem, but the flashing is either a new approach or a hack job. I have a metal roof and got some special silicone boots to flash my carefully limited roof penetrations (2). A flexible silicone boot seals around the PVC pipe. The boot is sealed to the roof with silicone caulk, a metal ring, and a whole bunch of screws. On my boiler building I used an all metal flashing for the chimney, overlapping roof panels and the flashing. I also position my boiler and the chimney so it landed in the middle of a roof panel.

 

[pen]

If I understand, it sounds like the pipe is below the roof and the metal is pounded down into it? If so, that is NOT correct and needs to be above the roof itself.

If it is that way, the concern is that water will flow down this and (I realize you are in Alabama so snow probably isn't an issue) leaves and/or snow or whatever could block a pipe that is lower than the roof.

Maybe I'm wrong and that is more common down south, but I've never heard nor seen anything like that up here.

I agree that a pic would help. But if I'm getting the jist of this, and it were my home, I'd be extending that pipe above the roof and putting the appropriate collar on it

pen

 

[semipro]

What you describe sounds like a lead roof jack installed over a PVC pipe. This is a setup I feel is superior to the polymer type roof jacks that are typically used nowadays as they depend upon an interference seal between the jack boot and the vent pipe. The lead type does not as it extends all the way to the top of the bent and then is bent over inside the vent pipe. The polymer types will crack with age and leak.

From what you describe it sounds like the jack was too big for the pipe (3" boot on a 1.5" pipe) but I'm not sure that's a functional problem.

A photo would help a lot.

 

[maple1]

I think Semipro has it figured...

...but we need a picture.

 

[Giles]

Thanks for all the replies--I have since found that this vent cap was just poorly installed. I simply used 12" slip-joint pliers and carefully pressed out the large wrinkels that were "essentually" making the top opening smaller.
I found that this lead cap is the best vent cap available---Just goes to prove that even quality material can be jepordized with uncaring workmenship
Previous owner stated that he had a roofer install the new roof about three years ago. After all---how many home owners will be on a roof to inspect ???