Vent stack leak and install question
We have a 3+ year old home. I am in the process of finishing the other half of my basement and a few weeks back I noticed an open vertically run "mystery pipe". I assumed it was a vent pipe, but since I'm not a plumber I didn't think anything of it.
About a week ago we were getting a nice steady rain and one of my kids noticed that there was a wet spot on the floor. Sure enough, it was coming from the open pipe.
I got up on the roof today and checked the flashing and flange. I sprayed water around the base of the pipe and no leak. I then poured about a 1/4 cup of water directly down the pipe and it came right out the bottom. We never noticed it before, but we didn't use that space much before and the amount of water isn't much under natural conditions so I'm sure it always dried quickly.
Sooo... what wasn't done correctly, and how do I remedy the situation now?
Obviously, I'll need to take care of it before I can drywall.
Thanks as always.