cutting into cast iron waste stack

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!
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It would be fairly cheap and easy to brace the existing stack before cutting. It is a whole bunch easier to help keep it from falling than to try to raise it back if it moves. PVC replacement is probably fine, but it is no big stunt to replace it with cast iron and no-hub clamps, or reinstall the piece that comes out if he is using a chain cutter.
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Huh -- I never even thought of that. You can replace it with the same piece? Or new cast iron? I didn't think they even did that anymore...
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snipped-for-privacy@yahoo.com wrote:

If the plumber is lucky, and the existing pipe doesn't crack, he may be able to reuse the piece. It is never a good idea to count on being lucky and the pipe being in good condition.
You can still get cast iron, and it is still used, but the bell-shaped hub connections packed with oakum and lead are pretty much relics of the past. Google Fernco to see what is generally used nowadays.
R
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snipped-for-privacy@yahoo.com wrote:

If not supported, the burden of holding the waste stack from dropping would be the connections of the drain pipes from sinks, tubs, and toilets to the waste stack. Unless there is some strapping somewhere holding the waste stack, I would be concerned too.
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Bill
In Hamptonburgh, NY
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wrote:

In older buildings they are usually supported at each floor by some steel welded to the side and bearing in the floor framing. It's fairly easy to confirm from below.
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MichaelB
www.michaelbulatovich.ca
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Hi everyone -- thanks for the replies.
Well, the deed is done. The plumber came over early, I asked him to please brace the pipe and he didn't object. He used steel strapping and a masonry anchor -- but still insisted it wasn't going to move. He decided to cut with a grinder/saw first, then finish with a Sawzall.
The cuts were made -- and the pipe never moved even a hair. Stood firm. PVC with a new, lower, clean-out was soon in place with neoprene gaskets/steel bands.
So, I guess this pipe was indeed supported at each level -- but those supports were not visible from the basement (finished ceiling). Plumber also said that since the sink, tub, and toilet of the 2nd floor bath tie into this stack -- all of those wyes are supported by the floor joists as well.
Everything seems fine so far. This was complete at 11:30am this morning (its now nearly 9pm EST) -- so I'm assuming I don't have to worry about the pipe crashing through all levels and taking everything with it.
These homes were built by German Catholics just before WWII -- they are built like tanks, and I guess the plumber just knew that the pipe was properly supported at each level.
Still a scary thought, though. But the cracks have been treated (reason for cutting the pipe in the first place), and the replacement PVC seems to be working fine.
Can I stop worrying now?
;-)
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