What's a Stack?

After the last post Marie asked, "What's a 'stack'?"

It's the big black pipe in the picture.  This one is cast iron, but they are often plastic in modern houses (see second photo).  From here it goes up into the attic and out through the roof to let the sewer gas escape.  That's why it is sometimes called a "stink pipe".

The toilet drain connects to it just below the floor level.  So from here the dirty toilet water goes down the pipe into the basement to the city sewer.

One of our new stacks is pictured in the second photo.  This one can't go straight up through the roof because that would place it too close to the attic bathroom window.  You don't want the "stink" getting back into the house...

At the very bottom of the picture feeding into the main pipe are the drains from the toilet and shower.moving upwards: on the right is the drain from the wet bar (long pipe running away from the camera on the right side of the picture) and the left is the drain from the bathroom sink.  At the top left is the bathroom sink vent which joins into the main vent running off the top right.

The third photo shows a similar arrangement from the old master bath.  The main vent stack from the first photo can be seen on the far left.  The rest of these pipes are old galvanized pipes: up from the kitchen at the left; sink's drain and vent in the center; tub's vent on the right.