Brace the hell out of cast!!!!!!!!!!!!! Cast iron is brittle and
cracking is too common.
the total weight is in excess of 500 #s and the potential leaks
include the roof (a soft lead sheild aove the roof line can and will
fracture).
There are special collars for such bracing, don't let him cheap out
and attempt to use iron or copper straps.
Also assure that this so-called 'professional' uses the correct snap
cutter. any other method could introduce vibration which could disturb
the oakum packing originally used (if this is hubbed cast iron).

BTW ask to see a copy of the guys license as a plumber. Bet he is not
licensed or he would not be having this argument.

On Mar 25, 8:30 pm, wrote:
I've got a plumber (who I really trust) coming out tomorrow to
temporarily cut into one of my main cast iron waste stacks. Reason:
there is a crack in the foundation right behind the stack that is
going to be treated tomorrow with epoxy injection -- and the stack is
in the way.

Once the crack in the foundation has been treated, the plumber is
going to replace the cut-out section of cast iron pipe with PVC.

My worries: the waste stack runs all the way up to the 2nd floor (and
out the roof through the attic, so technically through to the 3rd
floor). Everything I read says you MUST support the stack when making
a cut like this.

I asked my plumber (very reputable company and he has done alot of
work in this house for me -- all of which has been good) if he would
need to support the pipe before making the cut. He said "no" -- but if
when he began to cut he though it needed it, he would support it from
below (in the basement, where he'll be cutting).

I am worried about this. It's a beautiful 1930s Tudor-revival era
brick & mortar home -- built like a tank -- and I don't want to have
all kinds of damage to the plumbing connections in the walls that
connect to this waste stack when it gets cut (I hesitated even doing
this, but the crack in the foundation is something that appears to
have needed attention for a long time -- it gets water, although I've
fixed most of that problem from the outside).

Help. What do I tell my plumber? Do I insist that he install a brace?
Does it need to be a permanent brace? I can't imagine how tying in PVC
w/neoprene gaskets is going to support the weight of this stack. How
does this work? Should I be worried -- or trust this guy (who has 40
years of experience in this area, working on these types of homes)?

Thanks for any guidance you can provide!