Extending vent stack past snow

[DrBoom]

We've had a problem with a ceiling leak during larger snow accumulations that I'm reasonably confident is caused by snow covering one of the vent stacks and leaking from one of the vent stack joints in the attic. Unfortunately, the section of attic where I suspect the joint is a problem is far too confined for me to get in there and try to improve the joint.

Regardless, it seems prudent to extend the vent stack another 6-12" since it is my understanding that the vent should never be snow covered.

From the ground and what I can see from a distance in the attic, the entire vent stack appears to be PVC. It looks like maybe 3" diameter but I haven't yet climbed onto the roof to verify. From the ground, the two stacks in my attached picture appear to be different diameters but this may be an illusion from the distance.

Is there anything more complicated to extending the vent stack than adding an appropriately sized PVC coupler and short section of PVC pipe? I plan to climb onto the roof when we have a good weather day on the weekend to measure the pipe diameter but appreciate any advice or other things I should look for while inspecting the stack.

I've attached a picture of the relevant roof section. The stack on the right of the picture is the one I believe is causing (very brown) water on the ceiling but I plan to extend all 3 (another in a different section of the roof) while I'm at it.
Thanks, Jon (in southern NH)

 

[Reach4]

We've had a problem with a ceiling leak during larger snow accumulations that I'm reasonably confident is caused by snow covering one of the vent stacks and leaking from one of the vent stack joints in the attic.

Extending the vent would not prevent the leak.

You should have a roofer check things out.

One way leaks happen is an ice dam. The snow in the middle area of the roof melts quicker than the snow/ice near the downhill edge. Snow travels up between the shingles, and leaks in. Typically a sheet of tar paper is put under the the bottom several rows of shingles to stop the water that creeps up. Ther are more sophisticed membranes that can be used to prevent this leaking.

There are heated electric strips that are often put up over the shingles near the roof edge to let water flow down, rather than pooling.

Is there anything more complicated to extending the vent stack than adding an appropriately sized PVC coupler and short section of PVC pipe? I plan to climb onto the roof when we have a good weather day on the weekend to measure the pipe diameter but appreciate any advice or other things I should look for while inspecting the stack.

The PVC should be protected from the sun. This can be done with paint. If the PVC has been painted, I think the paint needs to be removed before gluing on the extension. I am not a plumber.

 

[Sponsor]

 

[DrBoom]

We don't have an ice dam problem. I can say this with high confidence because we did once upon a time and have put significant efforts in mitigating. In addition, we only have this water intrusion when the snow is above the height of the vent and only briefly. We can have lots of snow on the roof and water intrusion - only when the vent is covered. Also, where the water is coming in is clearly rolling down the vent piping.

Thanks for your assistance.

 

[Reach4]

In addition, we only have this water intrusion when the snow is above the height of the vent and only briefly. We can have lots of snow on the roof and water intrusion - only when the vent is covered. Also, where the water is coming in is clearly rolling down the vent piping.

If snow/water comes in thru the top of the pipe, it will move down the piping to your sewer/septic.

If water comes in at the base of the pipe, it will continue to do so if you extend the pipe.

Looking at your photo again, I think I see the problem. The roof flashing is usually a special shingle, and like a shingle, the top edge goes under the course above. Your black flashing appears to be setting on top of the shingle. Maybe it is a different design than what I expect, but if it is, it would require sealant to prevent water from running in.

 

[DrBoom]

We only have water intrusion when the top of that particular stack pipe is covered (snow height over the pipe completely covering it) with snow (like twice a year). The water isn't coming in through the boot or we would have a problem for the months the roof (and boot) is covered with snow each winter. I can't squirm close enough to it, to directly inspect the stack run in the attic, but there is a trap shortly before it penetrates the roof. I think that trap has a problem and is leaking a tiny bit when there is enough water that makes it in from the snow melt when the top of the stack pipe is covered with snow.
Thanks, Jon

 

[Tughillrzr]

Trap in the attic?

 

[Jadziedzic]

To which of the two vent stacks are you referring? That right-hand one looks like a boot commonly used by radon mitigation system installers, which does *not* extend under the shingles like a normal plumbing stack flashing does. The "sits on top" variety can be installed without climbing on the roof, which is a big plus for the guys installing radon systems. Our radon system has the same type of boot, and I was leery of it at first, but so far it hasn't leaked; fortunately it exits through the roof above the garage so no damage would occur from a leak.

Your mention of a trap there does seem odd, as those would not be used with radon systems. Can you add a picture or two of the in-attic piping?

You might consider having a roofer come out and install a traditional stack flashing there. We've had good luck with "Chick" Beaulieu roofing here in Nashua.

 

[DrBoom]

The below picture is from the attic. Clearly, no trap. That was my mistake as it was a while I climbed to that section of the attic. I can only assume that one of the many connections visible in this picture OR another one not visible in the walls or attic is the problem. The picture quality is poor because its quite difficult to get close to that part of the attic. This is not a radon mitigation system (we don't have one). As a reminder for those recommending a fix to the boot - the boot or bottom part of the pipe being covered with snow is not a problem, we only have a problem when the top of the pipe is covered in snow a couple of times a year.
Thanks for the help.

 

[Reach4]

The below picture is from the attic.

Is the fitting I pointed to with the yellow arrow open?

As a reminder for those recommending a fix to the boot - the boot or bottom part of the pipe being covered with snow is not a problem, we only have a problem when the top of the pipe is covered in snow a couple of times a year.

We understood you, but I continued to be skeptical.

If that fitting I pointed to is open, that could allow snow to enter and melt. Air flow could even blow some snow into that horizontal pipe. So is there an open fitting, or is that just a mis-reading of a fuzzy photo.

If you used a digital camera with a flash, and you are up close, try setting the camera to the "macro" mode. If you used a digital camera with flash and you are far away, try zooming to just show the area, rather than cropping a wide picture.
To take a better picture with a cellphone, some cellphones have a night mode that takes several pictures and integrates them into a single good picture.

 

[DrBoom]

I'm reasonably confident that the fitting is not open. The light flare is because that section of attic is very confined and I'm on a telephoto lens connected to my phone with a flashlight pointed down the section. It is very dark down in the confined section with additional light. I cannot wiggle myself close enough to completely confirm. I have no idea how they found someone to wriggle themselves into that section to finish the install. Nor how the spray foam installer (we have 2" of closed cell foam) squeezed himself in there a few years ago when we had that done.

We don't have a problem in heavy rain, only when the top of the pipe is covered with snow so I have to assume that it isn't just that water makes it in but some sort of vacuum/air flow effect of the top being closed off. As I haven't yet climbed onto the roof, there could also be something in the vent stack that blocks rain intrusion.

 

[Tughillrzr]

Get a roofer to double check vent boot. In Pictures pipe looks to be crooked but could just be the way you took picture. Around us 15-18” above roof plane is all it calls for. We get lots of snow. Extending will do nothing. Something with the snow in winter causing boot to leak.

 

[DrBoom]

Why do you believe the boot is at fault? We can go many weeks with the boot fully engulfed in snow without a problem and, then, have a leak for a day or two when enough snow covers the top of the pipe. I'm trying to understand what mechanism you are suggesting would lead to water coming through the boot only when snow has covered the top of the pipe.

Also, we have close cell foam insulation on the underside of the roof. That makes it extra difficult (certainly not impossible) for any water to make it through a roof leak. The water that we do see evidence of is very brown and only a small amount in 1 spot of the ceiling. That brown color has reinforced my thought that the leak is through the vent stack piping. I've never experienced a roof leak before that had colored water even if the stain was colored.

I appreciate your help in working through this.
Thanks, Jon

 

[Jeff H Young]

looks improperly flashed to me from the moment I saw it