Enter the stage: the drain-waste-vent system, short DWVS, also called "The Stack". This is the center pipe of your house's plumbing system connecting your vent at the top of the roof with the sewer at the bottom. This is the way your waste (grey water and unmentionables from your toilet) drains down and gases vent out the top.
We are blessed with a great contractor team, though, and they decided to check the stack out after all. Maybe it was still in great shape and we could use the saved money on something else? Something fun, like a restored staircase? So we played whack-a-mole upstairs were shorter sections made it easier to open up one part for a quick peek and easy replacement.
Yeaaah, see that stack? Notice how the center appears to be solid? Solid as in "nothing can go down" (or up)? Basically our stack was filled with corrosion on the inside and some parts of the walls were worn down card-board-thin. It -really- needed to be replaced.
[Come a little closer: a rusty corroded mess]
[Ding, dong, the stack is gone: looking up from the first floor all the way to the roof]Until the plumber gets to the Ugly Duckling to re-plumb our house we're left with a gaping hole where the stack once was but at least we're well on our way to a DWVS that won't explode inside our walls the moment we flush the toilet for the first time. You know, if it would have taken that long for us to notice that there is something seriously wrong with our plumbing.
There's one scary spot to explore left: What's hiding underneath all those layers of linoleum in the hallway and on the landing of the stairs upstairs?