If the roof is constructed so that there are sections that are not visible from the ground, look for a vent stack when you are conducting the attic inspection. If a vent stack has been installed, you will see a pipe coming up from the floor and going out through the roof.
In some cases, the restricted space and the lack of adequate lighting in an attic may make it rather difficult to check for the vent stack.
Plumbing Vent Stack Inspection – Plumbing Code Violations
According to the plumbing code, the vent stack should terminate above the roof. Sometimes, you may find a vent stack that terminates near a window or one that runs up along the side of the building – a common practice in the northern portion of the country. Just as with vent stacks that terminate in the attic, the ones that terminate near a window or that run up along the side of the building are in violation of the National Building Code.