Is the attached photo a roof drain vent that is coming through the ceiling? The pipe has always been there but with our huge rainstorms is now dripping water down into the room.
I would assume its a terminated vent from something before. Roof drains are not common in residential nor are they vented. It is probably holding water from the vent thru roof or condensation. You may want to go into attic and find it and delete.
To me it actually looks like a discontinued electrical conduit. It may have been sealed on the other end outside of the building and is now letting rain water through.