Soil stack and venting

[Tylock]

Hello, I have an old rental and the soil stack stops at the first floor bathroom with a toilet on top of it which can't be moved. I replaced the old toilet in the basement plus added a wash basin. So those openings that were unintended vents are no longer and nothing worked, total vacuum. I snaked out the trap vent outside that was clogged and installed vents on the three sink traps. Everything works, but not great. There is a 5 inch iron pipe outside that comes out of the ground. It's to the side of the toilet in the basement 3 to 4 feet away. This pipe runs up the side of the house 30 plus feet and ends 3 feet above the gutter. Nothing is connected to this pipe on the exterior of the house. Do you think this is connected to the waste pipe underground? I plan on cutting it down in pieces for scrap then run a snake through it. If this is the vent and it dose work do I have to run a PVC pipe back up past the roof? What do you think?

Thank you.

 

[hj]

I think your description is too convoluted to figure out what is happening, but the pipe outside, if it is a vent, is useless as far as your indoor piping is concerned.