"Jim Wilkins" fired this volley in news:mbt9mu$pih$1
@dont-email.me:

A buried pipe is supported against bulging out at right angles to
where the collapse begins. Yours wasn't.

Exactly how does that address "five story high vertical column separation"?

This stuff is not used only buried. It's approved (in some few places) for
vertical vents on DWV systems.

Lloyd