Toilet vent pipe causing moisture issue?

12 years ago

Hi all -

My husband and I just bought our first house this summer and discovered that the ceiling in a closet had peeling paint--finally went to scrape/paint and found that the ceiling in one corner is actually mushy. Went up into attic and found 2 things:

1) the fan for the bathroom (bathroom is on other side of wall from closet) is buried somewhere in attic--either under insulation or in between ceiling and attic floor and is not vented from what I can tell (we stopped using it!)

2) There is a rather large black iron looking (cast iron?) pipe running up through the attic to the roof and it seems to be very close to where the ceiling issue is in the closet. I was told by some (who did not actually see the pipe) that this is probably the toilet vent pipe. I noticed that there was some condensation droplets on the pipe in some areas, particularly the lower part where it gets close to the insulation.

While I know the bathroom fan is sure to be causing major issues and needs dealt with, I'm honestly leaning more towards the vent pipe as to the cause of the ceiling issue as it seemed to be right in the area where the ceiling issue is----does this make any sense at all? I told my father of my findings and he does not seem to think this pipe should be sweating/have condensation on it (not sure of proper term!)>

Any ideas? I'm planning to "dig deeper" this weekend, but providing it is this pipe, what can be done to stop the issue?

Thanks!!

Cassie

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Comments (4)

bus_driver
12 years ago
In cold weather the vent pipe might sweat from moisture migrating from the living area below. I would expose more of the pipe by pulling the insulation away from it. Except for possible fire hazard, spraying the outside of the vent pipe with urethane foam should solve the problem. Other effective insulation for the pipe should be researched. Of course, the inside of the pipe must be left unobstructed.
jakethewonderdog
12 years ago
Cassie

A couple of points:

1. The bathroom fan has to be vented through the roof or eaves. Having it vent into the attic space can cause condensation on cold surfaces (like the vent stack or wood framing)as well as mold and other problems.

2. It could be that the drops of water are condensation on the pipe - but that wouldn't be my first guess. The pipe would have to be significantly colder than the surrounding surfaces AND the humidity would have to be very high as well. What I have seen is that the vent is typically a little warmer because of hot water usage and because it's in a heated portion of the house before it exits to the attic. If anything, the condensation should be be closer to the roof. An exception might be if you are in a very cold climate (UP in Michigan, for example).

I would look for a small leak where the stack goes through the roof. It's not uncommon, especially with cast iron pipe, for that joint to leak. Cast iron pipe is rough on the outside and doesn't seal as well against a rubber boot on the roof - often they are just sealed with roofing tar - which dries out and cracks. Look for daylight around where the pipe goes through the roof.

A short-term fix is roofing tar if it's leaking. A longer term fix is to cut the cast iron pipe in the attic and use PVC pipe (very smooth surface) and a new rubber boot on the roof. Join the PVC with the cast iron pipe using a Fernco fitting. Be aware that cast iron is VERY heavy.
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brickeyee
12 years ago
"Cast iron pipe is rough on the outside and doesn't seal as well against a rubber boot on the roof - often they are just sealed with roofing tar - which dries out and cracks. Look for daylight around where the pipe goes through the roof.

A short-term fix is roofing tar if it's leaking. A longer term fix is to cut the cast iron pipe in the attic and use PVC pipe (very smooth surface) and a new rubber boot on the roof. Join the PVC with the cast iron pipe using a Fernco fitting. Be aware that cast iron is VERY heavy. "

Or have an actual lead boot installed correctly.
They last nearly forever, like the cast iron (especially old oakum and lead caulked cast iron).
clippillo.gmail.co
12 years ago
Thanks for the replies.
I'll check for a roof leak around the pipe. It had not rained in days when I had checked it and the moisture on it looked like when a pipe "sweats." We shall see. I'm going to have to go up there when it rains next time and really look if I can't come to any solid conclusions.

I think it did only have moisture down closer to the insulation, which I know someone said they didn't think was "normal." I'm wondering if there is a lot of moisture from the bathroom fan not being vented and it has made all of the insulation that soggy.....I THINK the bathroom fan was installed in between the ceiling and a solid floor up in the attic somehow (lovely, eh!?)...the solid floor has newer blown in insulation on top of it, but there is old insulation in between the ceiling & the floor. Possibly the moisture from the insulation is collecting on the pipe? I'll have to check it out in more detail this weekend and will let you know what I find. From my investigations last weekend, I did not find the bathroom fan---so in any case it is buried, whether in the new insulation or the old stuff under the flooring.

Thanks so much for the responses!

Cassie