I recently bought a home which was a renovation. I had a water leak from the ceiling in an upstairs room. Upon opening up the drywall, I noticed there was what appears to be a vent of some sort that is sealed at the top.

I noticed a new vent over the bathroom made of PVC. I see condensation on the inside of the rubber cap that seals the old black metal vent. Should I insulate the old pipe and wrap in plastic to stop any leaking, condensation or otherwise? Or should I remove the vent entirely?

  • 1
    Are we talking about exhaust vents (duct shrouds) or plumbing drain vents (pipes)?
    – isherwood
    Feb 14, 2019 at 20:43

1 Answer 1


If I understand correctly, you're saying that there is moisture getting past the seal on the old (metal) pipe's flashing, but not past the seal on the new PVC pipe. This is probably due to a failing seal, and not condensation. If the old pipe is abandoned, I'd do one of two things:

  1. Go into your attic and cut it off below the roof line. Repair the roof sheathing and roofing.
  2. Replace the flashing from above.

It's possible that you're actually seeing condensation if the attic has very poor ventilation and there's a source of moisture somewhere, such as a roof leak. In that case, fixing the roof leak should eliminate condensation.

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