Author Topic: Mystery pipe  (Read 4672 times)

Latwell

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Mystery pipe
« on: October 02, 2015, 03:42:23 PM »
Problem #1: I went into our attic to figure out why there is a very small leak occurring in our bathroom ceiling. There is a pipe that runs from the bathroom area and up through the roof. We've had a lot of rain this week so we believe the leak is from that pipe. I'm not sure what the pipe does but I'm guessing I need to either cut a hole in the bathroom ceiling to find which part of the pipe needs to be replaced or pull up attic floor to look down to the bathroom ceiling.

Problem #2: While in the attic, I decided it was a good time to check around and make sure the roof isn't leaking anywhere. Thankfully, it isn't (which is why we think pipe #1 is the cause of the bathroom leak). While looking around, I noticed a pipe just barely sticking out of the floor (maybe an inch) about a foot away from the edge of the attic. I went down to the level below and couldn't find any pipes and then went into the basement and also didn't see any pipes any where near that area of the house. I have no idea where this pipe goes or what it is for. I tried to go outside and see if it ran down there somewhere. No luck. Above that pipe lies the problem. There's mold. I'm not sure if it's new or if it's been there a while but I know I want to correct the issue before it gets any worse.


Any ideas would be greatly appreciated!

Edited to add photo of problem #2.
« Last Edit: October 02, 2015, 04:05:00 PM by Latwell »

dandarc

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Re: Mystery pipe
« Reply #1 on: October 02, 2015, 03:51:51 PM »
Probably a vent on #1.  Very important to keep the drains working correctly - keeps the traps trapping so you don't get sewer gases coming up through your drains.

No idea on #2.

Spork

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Re: Mystery pipe
« Reply #2 on: October 02, 2015, 04:42:18 PM »
#1 - as said, it sounds like a plumbing vent.  These should have some sort of flashing around them on the roof.  Often it is a lead tube that fits snugly around the vent and has a flange that slides under the shingles.  That's where I'd look -- to make sure it is flashed correctly.

#2 - the mold makes me think moisture, which makes me think it is either a bathroom fan vent plumbed into the attic or possibly a gas vent with combustion gases dumping in the attic.  Neither is optimal, but if it is the latter, I'd be sure to fix it, otherwise you may have CO up there as well as moisture.   

I've seen a number of houses where they just dump bathroom vents into the attic.  I am by no means a code expert... but I vaguely think this is a no-no.  (Someone will correct me or back me up.)  I know I put in new bath venting in a bathroom about 15 years ago and my comprehension of the code then was that it had to be vented outside.

paddedhat

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Re: Mystery pipe
« Reply #3 on: October 02, 2015, 05:33:00 PM »
#1 sounds like  a plumbing vent stack. This allows toxic gases to vent from the sewer pipes in the home, to the atmosphere. It appears that you are describing a leaking flashing (roof boot) on the roof. This is a collar and flange assembly that is lowered over the top of the stack and integrated into the roofing material. It can be lead, although in these parts it wouldn't be unless the roof is a century old. Modern versions typically have a rubber collar and tin or plastic flange. Yours simply needs to be replaced.

#2 is a bit of a mystery. All the evidence points to it being a vent for a bathroom fan, except for the fact that the pipe appears to be far more substantial than what would typically be. Typically this would be a thin sheetmetal "stovepipe". If it's a bath fan it will be obvious if you look, feel and listen to the open end while a helper runs the fan. You could even have them spray some scented bath spray into fan to see if the fragrance travels up the pipe. If it turns out to be a bath fan vent, you would need to get it vented to the exterior, for obvious reasons.  This could involve a vent cap cut though the roof, or sending the exhaust out a side wall or soffit. Be sure to run this vent in either sheetmetal or flexible metal ducting. It must also be insulated to prevent condensation.  OTOH, it may be just another sewer vent stack that some lazy bastard decided to end in the attic. This is real dangerous, as it could fill the attic with sewer gas. As you are inspecting the open end of the pipe, have the helper flush toilets and run water in sinks to see if you hear draining water, or smell sewer gas. If this is an unfinished vent stack, you can cap it with a "studor valve" or air admittance valve. This is a cap that will let air into the stack, but prevent sewer gas from escaping.

Spork

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Re: Mystery pipe
« Reply #4 on: October 02, 2015, 05:39:17 PM »

#2 .... It must also be insulated to prevent condensation.  ...

Off topic side question, but:  Is this always true?  None of my bath vents (or dryer vent) is insulated.   My attic is foam insulated at the roof line, so there shouldn't generally be much condensation other than the dryer, which has pretty serious temperature differences.   The dryer vent does condense/leak, so I guess I should insulate that minimally.  (I did the lazy bastard thing when I discovered it and put a drip pan under the low point.)

Latwell

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Re: Mystery pipe
« Reply #5 on: October 02, 2015, 07:32:03 PM »
Thank you everyone for the responses.

For problem #1: I don't think the issue is the roof or anything actually touching the roof. If it was the flashing, you would think the attic ceiling under the roof would be wet somewhere, but it's not. The attic is dry completely around that area. The only part that seems to be wet is under the floor boards of the attic. I thought this pipe might be for the sewer gasses as suggested by others. I think my project this weekend will be to pull up a couple boards to confirm my thought.

As for problem #2: this dang thing is definitely a mystery. It's definitely unrelated to a bathroom. The bathroom is on the opposite side of the house. I believe it's above the stove area. Maybe it was for an old exhaust fan to the stove area but the pipe was never taken out? I'm thinking of getting a string with something with weight on the end of the string and then feed the string down the pipe and stop the string when the weight at the end hits something/stops. This way I can see if it only goes a few feet to the kitchen area or if it goes as far as the basement (I doubt it'll go to the basement since there's no pipes down there on that side of the house).


paddedhat

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Re: Mystery pipe
« Reply #6 on: October 03, 2015, 05:19:25 AM »

#2 .... It must also be insulated to prevent condensation.  ...

Off topic side question, but:  Is this always true?  None of my bath vents (or dryer vent) is insulated.   My attic is foam insulated at the roof line, so there shouldn't generally be much condensation other than the dryer, which has pretty serious temperature differences.   The dryer vent does condense/leak, so I guess I should insulate that minimally.  (I did the lazy bastard thing when I discovered it and put a drip pan under the low point.)

I would imagine that in dry hot climates insulating isn't necessary. Here in the cold, humid northeast, it is a requirement, as the hot wet air will condensate and cause mold in the attic. Metal pipe or flex is a code requirement, and for a good reason. I had a fan that burned when the motor siezed. The fire left evidence of flames entering the metal exhaust flex tubing, but it self extinguished. Had it been installed with plastic flex, which is not uncommon, it could of easily ignited the ceiling joist it was attached to. I insulate using pre-insulated flex duct, commonly available in the big box home stores. I buy a piece of 4 or 5" and remove the inner spiral duct. This leaves a nice padded jacket with a outer metal foil sleeve. I slide the fan duct into it, and secure both ends with huge ty-wraps.

paddedhat

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Re: Mystery pipe
« Reply #7 on: October 03, 2015, 05:25:26 AM »
Thank you everyone for the responses.

For problem #1: I don't think the issue is the roof or anything actually touching the roof. If it was the flashing, you would think the attic ceiling under the roof would be wet somewhere, but it's not. The attic is dry completely around that area. The only part that seems to be wet is under the floor boards of the attic. I thought this pipe might be for the sewer gasses as suggested by others. I think my project this weekend will be to pull up a couple boards to confirm my thought.

As for problem #2: this dang thing is definitely a mystery. It's definitely unrelated to a bathroom. The bathroom is on the opposite side of the house. I believe it's above the stove area. Maybe it was for an old exhaust fan to the stove area but the pipe was never taken out? I'm thinking of getting a string with something with weight on the end of the string and then feed the string down the pipe and stop the string when the weight at the end hits something/stops. This way I can see if it only goes a few feet to the kitchen area or if it goes as far as the basement (I doubt it'll go to the basement since there's no pipes down there on that side of the house).

Interesting. Remember, nothing beats being in the attic during a heavy rainstorm, flashlight in hand, to learn more about any potential leaks. If the pipe you describe is a vent stack, it should be dry from the highest sink drain to the roof. So your issue may be totally unrelated, or not...................

No matter the original source of your other pipe, it looks like it is currently transporting a huge volume of air from the interior of your home and blowing it on to the roof sheathing. If it is an old stove vent pipe, unfortunately, you need to seal BOTH ends. If you only seal the top you run into an odd situation. Air will rise in the capped tube, lose heat and condensate, causing a slight drip and another source of mold.

Spork

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Re: Mystery pipe
« Reply #8 on: October 03, 2015, 07:35:24 AM »

#2 .... It must also be insulated to prevent condensation.  ...

Off topic side question, but:  Is this always true?  None of my bath vents (or dryer vent) is insulated.   My attic is foam insulated at the roof line, so there shouldn't generally be much condensation other than the dryer, which has pretty serious temperature differences.   The dryer vent does condense/leak, so I guess I should insulate that minimally.  (I did the lazy bastard thing when I discovered it and put a drip pan under the low point.)

I would imagine that in dry hot climates insulating isn't necessary. Here in the cold, humid northeast, it is a requirement, as the hot wet air will condensate and cause mold in the attic. Metal pipe or flex is a code requirement, and for a good reason. I had a fan that burned when the motor siezed. The fire left evidence of flames entering the metal exhaust flex tubing, but it self extinguished. Had it been installed with plastic flex, which is not uncommon, it could of easily ignited the ceiling joist it was attached to. I insulate using pre-insulated flex duct, commonly available in the big box home stores. I buy a piece of 4 or 5" and remove the inner spiral duct. This leaves a nice padded jacket with a outer metal foil sleeve. I slide the fan duct into it, and secure both ends with huge ty-wraps.

Everything is metal flex duct vented to exterior... just nothing insulated.  Maybe I'll at least go back and insulate the dryer vent.  It is the only one I know of that condenses.

Latwell

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Re: Mystery pipe
« Reply #9 on: October 03, 2015, 08:41:58 AM »
Thank you everyone for the responses.

For problem #1: I don't think the issue is the roof or anything actually touching the roof. If it was the flashing, you would think the attic ceiling under the roof would be wet somewhere, but it's not. The attic is dry completely around that area. The only part that seems to be wet is under the floor boards of the attic. I thought this pipe might be for the sewer gasses as suggested by others. I think my project this weekend will be to pull up a couple boards to confirm my thought.

As for problem #2: this dang thing is definitely a mystery. It's definitely unrelated to a bathroom. The bathroom is on the opposite side of the house. I believe it's above the stove area. Maybe it was for an old exhaust fan to the stove area but the pipe was never taken out? I'm thinking of getting a string with something with weight on the end of the string and then feed the string down the pipe and stop the string when the weight at the end hits something/stops. This way I can see if it only goes a few feet to the kitchen area or if it goes as far as the basement (I doubt it'll go to the basement since there's no pipes down there on that side of the house).

Interesting. Remember, nothing beats being in the attic during a heavy rainstorm, flashlight in hand, to learn more about any potential leaks. If the pipe you describe is a vent stack, it should be dry from the highest sink drain to the roof. So your issue may be totally unrelated, or not...................

No matter the original source of your other pipe, it looks like it is currently transporting a huge volume of air from the interior of your home and blowing it on to the roof sheathing. If it is an old stove vent pipe, unfortunately, you need to seal BOTH ends. If you only seal the top you run into an odd situation. Air will rise in the capped tube, lose heat and condensate, causing a slight drip and another source of mold.

I agree about flashlight in hand and looking around during a rain storm. That's exactly why I was up there. And luckily we dnot have anything really to store yet so the entire attic is empty.

You make a good point about needing the seal the pipe from both ends. I don't want to seal it from just the top thinking it doesn't really lead to anything anymore because I'm afraid it'll then cause mold to go in the other direction of the pipe.

zolotiyeruki

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Re: Mystery pipe
« Reply #10 on: October 04, 2015, 09:50:56 AM »
As for problem #2: this dang thing is definitely a mystery. It's definitely unrelated to a bathroom. The bathroom is on the opposite side of the house. I believe it's above the stove area. Maybe it was for an old exhaust fan to the stove area but the pipe was never taken out? I'm thinking of getting a string with something with weight on the end of the string and then feed the string down the pipe and stop the string when the weight at the end hits something/stops. This way I can see if it only goes a few feet to the kitchen area or if it goes as far as the basement (I doubt it'll go to the basement since there's no pipes down there on that side of the house).
I'm thinking #2 is the vent from your range.  That looks as much like grease as it does mold, although mold is certainly a possibility--there would be lots of moisture in the air coming off a stove.

guitar_stitch

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Re: Mystery pipe
« Reply #11 on: October 14, 2015, 02:09:02 PM »
#2 is awful small to be any sort of fan vent.  Looks like it's maybe 3/4" or 1" pipe.

You're going to need to be a careful detective to figure that one out.

zolotiyeruki

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Re: Mystery pipe
« Reply #12 on: October 14, 2015, 03:50:18 PM »
#2 is awful small to be any sort of fan vent.  Looks like it's maybe 3/4" or 1" pipe.

You're going to need to be a careful detective to figure that one out.
Ah, you're right--somehow I missed the sense of scale.

guitar_stitch

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Re: Mystery pipe
« Reply #13 on: October 16, 2015, 12:04:55 PM »
I've been thinking on this...  It looks like there may have been a fitting on the pipe at some point.  It also looks like this may be against an outside wall...  Is there any chance that the was a condensate or overflow drain for an air handler or water heater at some point in a past life?

If not, you could always stick an air hose or other sound source in the line and see if you can hear where it terminates at.

zolotiyeruki

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Re: Mystery pipe
« Reply #14 on: October 16, 2015, 02:56:02 PM »
I've been thinking on this...  It looks like there may have been a fitting on the pipe at some point.  It also looks like this may be against an outside wall...  Is there any chance that the was a condensate or overflow drain for an air handler or water heater at some point in a past life?

If not, you could always stick an air hose or other sound source in the line and see if you can hear where it terminates at.
That's an interesting thought!  In our area, condensate drains have to go into the sewer (not just drained to the outside), so it's possible that this line ties in with the sewer line.  That would provide a nice source of warm humid air to encourage the mold growth on the underside of the roof.