nicktheplumber
Wally,
You can cut 4″ CI with the Sawzall, but you will go through several blades doing it. I almost always use my Ridgid snap cutters for this sort of job, cause it’s quick and easy. I reserve the Sawzall for those really close-quarters cases where I can’t get the chain around the pipe with my close-quarters Ridgid cutter.
It’s possible to crack old corroded CI with a snap cutter, but it’s more of an issue with fragile “corked” clay pipe than CI, and it is more of a problem with horizontal runs that tend to remain wet. I can’t say that I’ve never cracked up a CI pipe with the snap cutter, but when I did the pipe was already shot and more of it needed to be replaced than the section I was splicing into.
Unless you’ve had experience and know the “feel” of a snap-cutter on CI, you’d do better with the Sawzall. A word of caution: the Sawzall vibrates a lot and is not guaranteed to not crack a weak pipe. You can minimize the risk by going slowly, letting the saw do the cutting without apply too much pressure, and replacing the blades when they get dull.
Good luck,
NtP
