Leak from Vent Pipe

[MasterPlumbersKeymaster]

Live in a three story home and noticed a PVC pipe in the basement with a very small, slow leak.

Called a plumber and we have determined that the pipe is actually a vent pipe, not a discharge pipe. The water is leaking where the pipe is angled in another direction, but the water is actually coming from above this fitting. Where the pipe enters the ceiling in the basement, there is a small area where the wood is obviously wet.

We have been unable to determine the source of the water. The vent pipe snakes up through house through two floors, the attic and the roof. Along the way it appears to pass behind the wall of the downstairs half bathroom near the sink, and probably behind the guest bathroom on the second floor which is right above the half bath. Unfortunately no way to tell if there are any angle fittings on the pipe to vent any of those sinks or toilets.

Did not get on roof, but plumber inspected the pipe in the attic, but no obvious signs of moisture. No signs of water damage in the walls or on the floors to date.

Stumped on next action plan. Any ideas or suggestions to at least begin elliminating possibilities? All sinks & toilets in these bathrooms have been caulked.

Thanks! Jason

[Robert Stephen MortonParticipant]

j.anderson. You said that the vent pipe goes in close proximity to a sink.
Did the plumber check to see if the vent was connected to vent the sink, if so you may have a blockage in the sink waste & the vent is acting as a waste.
This wouldnt happen in Australia as we must vent above the highest overflow of the fixture served.
Bob

[Retired plbg1Participant]

Sounds like you are going to have to cut a hole in the wall and see where leak is comming from.

[DwpecksrParticipant]

take a food dye or a dye made for locating leaks. put the water dye mixture in one fixture at a time. check after putting dye in fixture for it to appear in the basement.This must be a drain line or a wet vent for a fixture for it to get water in it.

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