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Vent pipe roof leak

Posted: Thu Oct 28, 2010 9:45 am
by Bunky
I went over to my property today and the ceiling was wet, well after checking out the situation I found that the kitchen sink vent pipe is cut off below the roof, Does anyone happen to the know the size of this pipe ???

Re: Vent pipe roof leak

Posted: Thu Oct 28, 2010 10:02 am
by JD
Most homes are plumbed with 1 1/2" ABS pipe for venting. I have seen a few that were 2", but we are talking 1% or less of the 1000 or so roofs I have looked at over the years.

If you need to, you can enlarge the hole so you have 1/2" clearance around the pipe and add a couple and short piece of pipe. On metal roofs I like for the pipe to be a little long and then cut it off after I glue it in, I will cut it 1 1/2" above the roof line and install a metal vent cap.

Re: Vent pipe roof leak

Posted: Thu Oct 28, 2010 11:05 am
by Bunky
Thanks JD Do you screw this type of cap to the roof or just caulk it.

Re: Vent pipe roof leak

Posted: Thu Oct 28, 2010 5:21 pm
by JD
I put a big bead of roof caulking under the screw flange and install it with #10 hex head screws. The sealant will ooze out all around the vent. I use that sealant and little more from the caulk gun to seal the top side. Make sure the roof surface, the bottom and top of that vent cap's flange are lacquer thinner clean. New galvanized vents will have a film of production oil on them. This must be cleaned off or the sealants won't last very long. If the roof metal around the pipe is really goobered up with old sealants, you might consider getting a bigger vent cap to be able to screw into better metal.

Re: Vent pipe roof leak

Posted: Thu Oct 28, 2010 6:34 pm
by Bunky
Thanks JD

Now i just need to either find some abs to glue to couple to the lower piece or cut the vent down below so I can pull it out and rubber couple it to some PVC

Re: Vent pipe roof leak

Posted: Sat Oct 30, 2010 9:59 am
by Lookingforwork09
Roof venting can be hard, but the suggestion above is right on the money. You want to make sure this get sealed properly, and we all know how hard it is to work with something that was done improperly to start. Cut out the clearance and add the stub. I have never seen 2" piping, but it could depend on the code where you live.

Re: Vent pipe roof leak

Posted: Sat Oct 30, 2010 10:50 am
by Bunky
Well my problem was that the strap on the drain pipe broke and the pipe slid out of the existing roof cap, the top of the cap was broke off so I just put a screw through a pvc cap and crewed it on there...

Re: Vent pipe roof leak

Posted: Sat Oct 30, 2010 3:30 pm
by Bunky
Here's a photo of what I did

Re: Vent pipe roof leak

Posted: Sat Oct 30, 2010 3:46 pm
by JD
If your plumbing vent pipe slid down because a strap came loose, you might want to check the horizontal 3" ABS under the floor that it is connected to. This pipe should be strapped to the framing every 4'. The plumbing vent should not be able to slide down in the first place. That horizontal 3" pipe under the home should be straight and have a 1/4" per ft drop. If your vent pipe was able to drop inches down into the hole, you could very well have some plumbing drain problems in the near future.