I had a plumber in friday to replace three corroded shutoff valves in the basement (one being the main). Saturday (yesterday), I went downstairs and noticed a small puddle on the floor. I looked up and there was a pipe directly above it that was dripping. (pic below) It looks pretty corroded, but I've owned this home for 6 months and never saw a drip there before.

I can't figure out what it's connected to. The pipes for the kitchen go up one side of the house and the plumbing for the bathrooms and the sewer line runs up the other side of the house. this is almost directly in the middle of the house. I figured it was just an old line leftover from a remodel. So, I duct taped it to stop the drip and was planning to call the plumber back on Monday to cap it off.

Today I come home and immediately upon opening the side door, I smell sewer gas. It doesn't smell upstairs at all. just in the basement and stairwell leading from it. I checked the sewer line in the basement. No leaks are apparent. The basement toilet still has water in the bowl. Can't figure it out...then it hit me...did I tape off a pipe that connects into the sewer vent?

In retrospect, we did have a colossal amount of rain friday night and saturday morning. Could that have caused a drip in a vent (if this is a vent)? Or perhaps the plumbers shook the piping just enough to loosen something upstairs...I just can't figure out where this line goes or what it would still be connected to. I've also got an open pipe sticking up along side the house. I looked all over that part of the basement can't tell where it comes into the house (if it does), but perhaps it's related? It looks like the same kind of pipe.

Any advice would be appreciated. I know nothing about this stuff. I'm just sitting here waiting to see if, after removing the duct tape, the smell (and drip) continue or not...

thanks in advance

Open pipe in basement:

Open pipe outside: