Roof Vent Pipe - add a cap?


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Old 07-11-17, 01:19 PM
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Roof Vent Pipe - add a cap?

I *think* I've finally figured out the source of an occasional small drip of water from my powder room ceiling. I believe it is actually caused by a leak in the PVC pipe used for the air vent thru the roof. Since it only seems to happen when we have a very heavy rain, I think either the pipe was not joined properly or was somehow damaged when the house was built. I've measured and determined the pipe goes down inside the exterior wall on the 2nd floor, then turns across the ceiling of the 1st floor powder room, then turns down again and goes into the main line.

I don't really want to tear open the ceiling, so was thinking of adding some type of cover. I came across this link: http://www.doityourself.com/forum/pl...ts-roof.html#b that suggested putting a 180 on the pipe, but wonder which would be better - a cap or a 180 or a Tee or ....
I've thought about sticking a garden hose down the vent pipe to see what happens, but am: (a) lazy at the moment, and/or (b) pretty confident my guess is correct.
Thank you for any suggestions!!
 
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Old 07-11-17, 03:59 PM
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It's more likely that the rubber gasket on your roof vent pipe boot has failed.
 
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Old 07-12-17, 12:00 AM
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I'd bet dollars to donuts that XSleeper is correct -- it's almost certainly a roofing/flashing problem. You can confirm it with your hose. But if you want to put a 90 and a street 90 on the end and have it pointing down, there no harm in that. Try the hose first.
 
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Old 07-12-17, 05:20 AM
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95% of the time the leak is from the boot around the pipe where it penetrates the roof. However I did have a similar problem on one house and up in the attic I found one joint in the PVC vent piping that was not leaking and the source of a slow leak during heavy rain.
 
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Old 07-12-17, 06:20 AM
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I agree that it's most likely the boot. Post a picture and someone may be able to help spot a problem. Could be that it's bad, or could be that it wasn't installed correctly, either initially or as part of a second roof. Either way, it shouldn't be too much of a job to make it right.
 
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Old 07-12-17, 06:21 AM
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Thank you all for the 'boot' idea, but I had the roof replaced two years ago (and had the leak a week ago). Roofer installed new boots, and I also did the trick of having them add an additional rubber boot cut-out over top of their boots to buy some more life from them. Steve-Gro, do you think I would need a screen to prevent wasp nests, or would the pipe (2 or 3") size not interest them?

I guess I will crawl my lazy butt up on the roof with the hose just to make sure

Thanks Again!!
 

Last edited by Wayne G. Dunn; 07-12-17 at 06:51 AM. Reason: typo
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Old 07-12-17, 02:49 PM
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A picture might still be helpful. I'm sure we've all seen "roofers" that screw up around boots.
 
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Old 07-12-17, 11:04 PM
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I don't recall seeing vents with a screen over them, and I haven't seen any insects in any of them, so I think a screen would be superfluous.

Why not give the roofer a call?
 
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Old 07-13-17, 05:32 AM
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Have you actually been up on the roof to inspect your boot? It is possible there is something up there that is installed improperly.
 
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Old 07-13-17, 07:02 AM
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This little task just got bumped down a notch as I discovered a toilet flange leak in the powder room (maids removed my shims!) so need a couple hours to reset that thing <groan>

Thanks again to all of you!!

Yesterday I tried pouring a couple gallons of water into the pipe, but naturally there was no leak. Later today I will get the hose out and flood the inside of the pipe and around the boot and flange area. I've attached two pic's... note as mentioned earlier, there are TWO rubber boots on each vent pipe. The leak issue was happening long before the roof was replaced (and the roofing co. does excellent work).

I could also cut a hole in the sheet-rock in the garage where the leak is (shares wall with powder room) to see if I can tell the direction the water comes from.

The following shows the pipe that I think is the culprit - it comes straight down from the roof into the basement and when it passes by the powder room, it is about 3 feet from the point of the leak.
Name:  vent_pipe.jpg
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Size:  50.3 KB

There is another vent pipe about 10 feet further to the right of the first, but that pipe doesn't come near the leaking area (yes, I understand that water can run along pipes, rafters, etc.)
 
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Old 07-13-17, 03:02 PM
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Get rid of that blob of caulking on the left... water needs to be able to freely run around the gap between the shingles and boot shoulders.
 
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Old 07-14-17, 10:25 AM
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It looks like the boot is in good condition... but water has a way of finding its way into all sorts of tiny cracks and crevices. The fact that it didn't leak when you put the hose into the pipe leads me to believe that it is a boot sealing issue. Running a hose for a few minutes is way more water than would ever find it's way into the pipe from rain, so I think you would have definitely noticed a leak if the pipe itself was damaged.

Good luck with your next test!
 
 

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