Here's a weird one; stink stack condensation leak in house

[Scott V]

Thought I'd throw this out there for any ideas; bought my current home last summer June 2014. Completely redone tri-level. 3rd floor was added in the 90's. Saw a patched area on the living room ceiling when we bought it. Somewhere around September we noticed a water stain developing on the ceiling in this area. Stopped using any plumbing in master bath above this area. Tore it open a couple months later and saw this was a trouble spot for PO. Tried running water in toilet, sink and shower one at a time and could not get the leak to happen again. Stapled some white poster board over the ceiling. Never saw it again, UNTIL about 2 weeks ago. Realized it happens when the outside temperature has a big swing overnight resulting in heavy dew on everything outside in the mornings. (we live close to Lake Michigan) Dropped poster board and taped it to the floor. Sure enough, drip, drip, drip every morning at 5:00 AM for a few days. Looked a little closer and it is clean water running down the outside of the vent stack going to the roof.

So we have determined that is happens ONLY when there is heavy dew outside at dawn. Rain doesn't do it and plumbing fixtures don't leak. Looked at vent pipe up in the attic and it takes a bend across the attic before going through the roof. No moisture on outside of PVC pipe anywhere in the attic. Have determined that is happening in the wall upstairs between the 2nd floor ceiling and attic. How the hell is this happening??? Anyone ever seen anything like this?

 

[ilovevocs]

It sounds to me like you have diagnosed it as a condensation issue.

The pipe is condensating due to a temperature differential across the pipe. The pipe is colder than the space around the pipe.

With out trying to dig into the functionality of the structure too much the quick fix would be to just insulate the pipe.

Personally though, i would try to find the true source of the issue. You have moisture charged air contacting the pipe at some juncture and the pipe is colder than the air around it. Condensation occurs on the warm side. So what is making the pipe cold and or where is the moisture charged air coming from?

I'm trying to provide some feedback without getting to in depth into theory.

 

[HoosierMark]

First thing would be to seal the area around the vent pipe where it turns down into the wall. Moist air apparently is getting in somewhere. Could it be that when you shower or run hot water the warm air is venting upward and warming the pipe. The outside is cool which results in the condensate. Please post when you have a solution. I had a somewhat similar issue with a bathroom vent fan pipe. It had a low spot in it and when the warm air cooled it created water and eventually leaked out and created a wet spot. When we raised the center of the air vent pipe the problem was solved.

 

[sixty4]

I would bet there is a hole in the vent line somewhere above via drywall screw. I would look directly behind the toilet at where the trim nail was shot in as well. Also if you have crown molding check that area as well. A stud detector may help if you can't see any signs of a head (you may pickup nailing plate but worth a shot).

 

[Scott V]

Thanks for the ideas/theories. Sixty4 that is the latest idea we are pondering!

I had a plumber look at it and his thought was maybe we put a hole in the vent stack with the picture hanging on the wall upstairs. That proved false, but leads me to believe maybe there is another hole or bad glue joint where inside condensation is getting outside the vent pipe. I'm guessing I'm going to have to open the wall on the third floor hallway in the pic. Would be easier than removing the toilet to do so in the master bath.

 

[sixty4]

Thanks for the ideas/theories. Sixty4 that is the latest idea we are pondering!

I had a plumber look at it and his thought was maybe we put a hole in the vent stack with the picture hanging on the wall upstairs. That proved false, but leads me to believe maybe there is another hole or bad glue joint where inside condensation is getting outside the vent pipe. I'm guessing I'm going to have to open the wall on the third floor hallway in the pic. Would be easier than removing the toilet to do so in the master bath.

I had one like this several years back, drove us nuts. We ended up opening up the same as you may have to do. The sheetrock guy nicked a hole in the pipe it rotted out and started to condensate. Check trim areas before opening (we were not that lucky). All the best!!

 

[Scott V]

Cool thanks. Weird ****!

 

[404]

Not criticising the OP here, but:
Is joining 2 vents in the attic before exiting the building legit in the first place? What is up with all that un supported steel conduit?

 

[larry4406]

Lack of kick plates and wounding of dimensional joists by drilling implies a hack plumbing job to me when the 3rd floor was added. Permits? Check roof boots very carefully; some literally need roofing caulk applied to pipe.

 

[ratdoggy]

Not criticising the OP here, but:
Is joining 2 vents in the attic before exiting the building legit in the first place? What is up with all that un supported steel conduit?

I was looking at the pipes (green?) that go through the joists...
Aren't they too close to the bottom of the joist?

 

[HeelSpur]

I was looking at the pipes (green?) that go through the joists...
Aren't they too close to the bottom of the joist?

Heck yes, he basically has nothing but 2x4's for floor joist. Center 1/3 is the norm.

 

[63spyder]

The green looks to be pipe insulation, water pipes? Probably fairly small holes

 

[Scott V]

Just asking if anyone had similar condensation issues with a vent pipe.

I can appreciate constructive criticism but I purchased this home the way you see it so cannot account for the work already done that is behind drywall.. It was a foreclosure in 2011 and picked up by a contractor then completely flipped and put back on the market. The craftsmanship I can see in the home is done well.

 

[Scott V]

The green looks to be pipe insulation, water pipes? Probably fairly small holes

Yes they are copper water lines with foam insulation around them. I guess they did that when they couldn't figure out where the condensation was coming from.

 

[Scott V]

Not criticising the OP here, but:
Is joining 2 vents in the attic before exiting the building legit in the first place? What is up with all that un supported steel conduit?

Can't answer your questions. Smaller vent pipe is coming from kitchen area. How should the conduit be supported? I'd like to revise it if it's an issue...

 

[CNGsaves]

If you're going to re-do the vent pipes, they should be 2 holes in roof straight up.

Get rid of that cobbled up shared vent pipe.

 

[Scott V]

If you're going to re-do the vent pipes, they should be 2 holes in roof straight up.

Get rid of that cobbled up shared vent pipe.

Thanks. Could local code dictate that the exit to the roof be at a height near the peak? There must be a reason they ran the exit closer to the center.

 

[CNGsaves]

^ ^ Possible. Honestly every house I've roofed had multiple vent pipes and many low on roof like yours would be. Your larger vent on right side of picture might conflict with rafters straight up, but that could be handled. Need to get GJ plumber chime in to know for sure on your strange "shared vent" setup.

 

[404]

Can't answer your questions. Smaller vent pipe is coming from kitchen area. How should the conduit be supported? I'd like to revise it if it's an issue...

I apologize, I do not mean to be a pain in the ***. IMO that conduit should not even be there, I wonder what kind of wire is in it.
I do not have the answers to my questions. Again, no irritation intended.

 

[Charles (in GA)]

I apologize, I do not mean to be a pain in the ***. IMO that conduit should not even be there, I wonder what kind of wire is in it.
I do not have the answers to my questions. Again, no irritation intended.

The OP is in Morton Grove, Illinois, and I do know that Chicago, and some other cities and counties nearby require all wiring in conduit. It goes back to when the cow kicked over the lantern and caught the barn on fire.

Charles

 

[larry4406]

It is quite common to tie vents together in the attic. This reduces the number of roof penetrations and thus possible leak points. I'm not a plumber but I do build houses for a living so that does not alarm me.

Note on the vent piping what appears to be an absense of purple primer. You may very well have a leak on one of the vent pipe fittings which creates the problem observed.

The waste piping at the exposed ceiling shows generous primer application.

Vent stacks route considerable condensation from moist humid air (showers, baths, etc). Condensation also forms when the vent enters the unconditioned attic space. This may be leaking from one of the un-primed fittings.

I have done "peppermint tests" to find plumbing vent/waste leaks. At the pharmacy you can buy peppermint oil (not cooking isle at grocery store). The oil is highly concentrated and mixed with hot/warm water and poured down the vent stacks from the roof side on all stacks. Then the stacks are temporarily capped off with test caps.

The intense peppermint smell will soon become evident at the leak.

I have even run garden hoses one by one down the roof stacks trying to find leaks.

Hope this helps.

 

[CNGsaves]

^ ^ IF . . . the OP's shared vent is strictly air venting or sewer gas, then likely no problem with the long nearly horizontal shared setup. However, OP is getting leaks and that long horizontal run may be contributing to his leaks (ie allowing any moisture to condense BEFORE it gets to top, along with poorly glued connection).

OP . . . tell us what all vents are combining in that shared setup ?? Are bathroom exhaust fans pushing lots of moist air in there ?? Where do all the bathroom exhaust fans vent to ?? Is there a kitchen stovetop hood vent also tied into that shared nearly horizontal vent setup ??

 

[Mad Dog]

Well, this is like deja vu all over again. We had exactly the same problem and I troubleshot every angle mentioned including leaking boots on the roof, etc etc. Ours turned out to be condensation on the inside of the vent tube which would occasionally leak from a bad glue joint on a tee. The tee was in the wall on the main floor and the leak was on the finished ceiling in the basement. After much angst I figured out the tee was in a wall behind a vanity and mirror. Tore it out and found the leak. Re-glued and no more problems. All along I thought the condensation was on the outside of the vent but it collected inside the pipe above the fitting and leaked to the outside of the fitting then dripped down the outside of the pipe and then off an elbow above the ceiling. Hope this saves you the weeks of aggravation I experienced!

 

[Gerald O]

Shared vent pipe may be ok depending on fixture count.
I'm betting on a poorly glued or not glued vent joint. Looks like several of those joints are not properly primered. Moist outside air is drawn down inside of vent and condenses on inside vent walls. It then dribbles down inside until it finds the bad joint and leaks out.

 

[egdede]

Perhaps the original installer glued himself into a corner?

When installing pipe, I have (I must admit) fitted pieces, started gluing at one end, and come to the end of the run to find that I can't remove the last fitting to glue it without making a cut and adding a coupling elsewhere!

 

[Scott V]

Thanks for all the info and tips. And it's funny to read that others have pulled their hair out over weird condensation leaks from vent pipes. The funny thing is that it didn't do it for months and now all of a sudden with outside temp swings it starts happening again. It was dripping again this morning. The one plumber I had look at it briefly (was installing my sump pump back-up system) was really intrigued with the whole thing and wanted to rip open the wall that day out of curiosity. He was more into that than putting my sump back-up system in.

From what I can see there is a secondary smaller vent stack (as seen in the attic photo) coming from the kitchen that is joining the larger stack going to the roof. The exhaust fans all have their own venting to the outdoors, including the one in the kitchen. And the 2 lower bathrooms are on their own vent stack on the other side of the house. However there is a 2nd HVAC unit in the attic. (The coil run off drain goes out the other side)

I'm strongly leaning towards a hole or bad glue joint in vent stack in the wall upstairs in the 3rd floor photo. We will have to open up the wall. We want some new paint work done over the winter so that will be a good opportunity.

And on the electrical code; Yes conduit is required everywhere in Cook County. No Romex allowed. BX can only be up to 6 foot whips.

 

[HoosierMark]

Now that you have mentioned the 2nd hvac in the attic, look around it and see if there is any moisture present. I had one condensate drain clog on a second floor apartment and the water showed up about 15 feet away on the steps. I am not sure how it got there but on the second and third steps there was water. Went looking for it and found a clogged condensate drain. Only thing I can figure is that it went into the floor at the wall and followed the path of least resitance. But to come out on a second and third step was odd.
You may have a clogged drain, nothing to lose by looking.