I have to cut off a section of cast iron waste pipe in my attic to tie
in a vent .My concern is when I cut off the section of pipe, the
weight of the upper part of pipe would cause it to possible come
loose from the roof flashing and sink, thus causing a roof leak. The
last thing I want to do is open up a can of worms by doing this job. I
was wondering if I should be concerned or if anyone else has done a
job like this, what advice to offer. Thanks