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Sewage Vent Pipe Leak

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NKLinwood

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I noticed recently that there was water running down the outside of my cast iron sewage vent pipe that runs from my basement straight up through my roof. I’m able to access to pipe right before it exits my roof via a crawl space in my finished attic. I can see a small amount of water slowly moving down the outside of the pipe. Initially I thought the issue was a leak in the boot, but I had this replaced and there is still water on the outside of the vent pipe. My suspicion is that this may be condensation from the cold air in the pipe, and warm air in the attic. Also, the problem seemed to start as the temperature dropped, and I’ve noticed water dripping down the pipe when it hadn’t rained or snowed. Any suggestions as to how to combat the condensation or other possible causes? Pics attached.
 

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Jeff Handy

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The humidity in the attic, or whole house, might be too high.

You could also cut that cast iron as low as possible, and change to pvc, which does not conduct as much cold from the outside.

Kind of overkill, but you could wrap heat tape or de-icer cable around that top portion.
Or just put a little fan blowing softly on the pipe, it will warm it up and also dry it off.
 

NKLinwood

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Thanks for the reply Jeff. I think I’ll give the heat tape or de-icer a try. I’d like to avoid cutting and replacing the top period with pvc for now, but may have to go that route if the problem persists.
 

Jeff Handy

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Keep checking back onto this thread.

You will likely get more advice, maybe better than mine!
 

Jeff Handy

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BTW, I would suggest insulation around the pipe, but I think it would just get saturated.

Maybe others can advise about that.
 

plowking

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How damp is the attic? Maybe ridge or roof or soffit vents might help A dehumidifer might work but where would you drain it and could be more maintence..We don't have cast iron in newer homes so don't see that here .I had a condensation problem with my bathroom with no windows ,had to put in a larger ceiling fan to the soffit to get rid of moisture from the shower. Actually my water well tank and softener system had major condensation in the basement.I wrapped them with insulation and it stopped it. Insulation may cause other problems but my softener tanks were fiberglass. The do make cupola fans for leachfield vents but don't know if it would work on the roof.
 
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