How would you suggest cutting a 4" cast iron drain pipe? Thanks!

You can use Sawzall with "Grit Iron" blades, "Snap Cutters", or "Chain Cutters". Your cheapest way out of it would be either to rent a pair of snap or chain cutters, or buy the grit iron Sawzall blades. Depending on how much cast iron you're going to cut, just be prepared to be there for a while if you are making more than 2 cuts through 3 or 4 inch pipe with the grit iron blades, Good luck,

John

First question... is it a vertical cast iron stack or a horizontal cast iron stack?

If cutting vertical stack then there are very special rules to cutting into these pipes because you need to worry about the vertical load that is above the cut... if this is the case and you want to discuss vertical stack cutting post back and I will go into details. Can also click on this link and scroll down to post #3 for more information and safety precautions:

https://www.askmehelpdesk.com/plumbing/new-basment-bathroom-252241.html

If this is what I suspect and connects into another question you posted (I also answered that post) then I am guessing that you want to know how to cut into the horizontal cast iron pipe and then how to transition from cast iron to PVC... am I close?

Like John said... there are a few ways to do this. For most homeowners I recommend using a sawzall and a carbide tipped sawzall blade (Lennox makes a great diamond sawzall blade but you probably can't find it)... simply the safest way to go especially when you consider the fact that the next tool for this is famous for crushing some of the cast iron...

You can also rent a ratchet chain cutter (1st pic.) or a snap cutter (2nd pic.). These wrap around the pipe and you ratchet handle or twist knob to cut pipe. They usually work great but can crush the pipe or cause linear cracking of pipe which could cause issues back to the vertical stack... and you don't want to start messing with the vertical stack... so probably best to go sawzall and carbide blades.

To transition from cast iron pipe to pvc pipe you will need to purchase a shielded clamp, commonly referred to as a mission or proflex shielded clamp... see picture. Any other clamp that you see at home depot is really illegal for what you are doing... ok? If going from 4" cast iron, then purchase a 4" cast iron x 4" pvc shielded mission clamp, then buy a 4"x3" flush bushing and install that into the pvc end of clamp. Pipe 3" to the toilet, 2" to shower, etc...

Let us know if need more information here...

MARK

How would you suggest cutting a 4" cast iron drain pipe? Thanks! John had it right and Mark and I are posting on top of each other again.
There are several ways to cut 4" cast iron. Snap cutters for a horizontal pipe and ratchet cutters for a vertical one. When cutting into a vertical stack you must support the upper section or it could fall and if that happens it could ruin your whole day. Good luck, tom

I cut iron pipe 4" and under with a portable band saw. It is much faster than a sawzall. You can probably rent one. If you rent one, make sure it will go on about 4-3/4" diameter pipe. 4" is right at the limit of most portable band saws.

On larger cast iron, I use a gas-powered concrete saw with a diamond blade for metal cutting. It is effective, but a lot of sparks.

Hi Albin...

By a previous post I am pretty sure that dreamduv is talking about cutting cast iron pipe that is already in place between joists, etc...

I'll tell you though... band saws are great, but I still think I can beat any saw with a good alligator snap cutter and on larger pipe we just add an extension chain and can cut pretty large pipes... although the ends won't be as pretty as yours... ;)

Just wanted to post that to keep dreamduv from using a gas cutoff saw inside the bathroom!!

Good day!

MARK

Mark,
Yep, you're right they probably can't use the band saw for that application. And, they darned sure can't use the gas saw! The thread didn't say what the application was.

I use these methods doing water treatment plant work... a whole different ball-game.

I appreciate the tip on extending the snap-cutter. I always get concerned about a snap cutter damaging the cement-lined pipe. Since I usually don't know if it is cement or epoxy lined, I try to keep it clean.
Al

I don't blame you there, AL. Gas cutoff is always best for concrete or epoxy lined pipes!

Have good day

Mark

Mark, Al and Tom... Thank you all for the terrific amount of information. My husband is so glad that I found this web site! When he has a minute, he'll take the time to sit down and read all of your postings. You are all great guys to take the time to help out. We'll keep in touch, as I'm sure we'll have more questions. Good Day Gentlemen, Kathy

Hey Kathy,
Thanks for the nice words. If we can ever be of service in the future we'rer as close as a click. Have a great Sunday. Tom

I used a Lenox 8" Diamond reciprocating saw blade for cutting 4" cast iron. It only took about 10 minutes and that was using Craftsman 19.2V cordless saw. I did have to change batteries a few times, but I already had 6 charged batteries ready. I would recommend to do it this way.

YUP! I mentioned that blade back in my original post (#3), but that lennox diamond reciprocating saw blade isn't always easy to find locally.

Since I found it and it is so readily available in my area it's the only way I cut cast iron that is in place.

Thanks, Mike...

Mark

Mark your previous post was very helpful for me and I appreciate your willingness to share your wisdom with us DIYers. I was able to find the Lenox blade at Lowe's for about $14. If it wasn't for your info I couldn't have done it. Thanks again.

Mike

Hey Mike! Thanks for taking a minute to post that... always nice to see our work appreciated!