View Full Version : Cast Iron: Cutting and joining to PVC

05-28-2005, 10:22 AM
Two questions regarding my cast iron drain line:

1: What is the best way to cut a 3" cast iron drain in the crawl space(15"). A sawsall seams to be the logical and most efficient way, but I'm not sure what blade to use. Or should I rent a chain cutter.

2: What is the best method for joining 3" PVC to 3" cast iron drain line. The drain line is about 2" below the surface of the dirt in the crawl space.


Mike Swearingen
05-28-2005, 11:08 AM
Snap cutter

You can use a snap-cutter, but I would use a reciprocating saw with metal-cutting blades. Cut it as straight as possible.
Connect the PVC to the cast iron with a no-hub coupling (aka Mission coupling), which has a neoprene rubber sleeve covered by a stainless steel sleeve with torque bands to seal it. You can get them at any plumbing supply.
Good Luck!

05-28-2005, 07:08 PM
Thanks. Does the coupler have to be covered in stainless steel?

05-28-2005, 07:32 PM
Yes, if you want it up to code...and to last. One style is a neoprene sleeve with hose clamps at either end. This is prone to abrasion, Flex, and (eventually) degradation of the sleeve. The other is also a neoprene sleeve, but encased in stainless steel and multiple clamps to distribute the pressure - the neoprene is just used as a sealer, the strength is in the metal. The other relies on the rubber for all of the strength of the joint.

05-28-2005, 09:07 PM
I like the snap cutters MUCH more than a recip. saw even with blades made for cutting cast iron. Just seems to be quicker and easier...for me at least. Of course, there are situations in which you cant get the chain around the pipe to snap it. In those cases I sigh heavily and go get the sawzall. lol

Good luck!

05-29-2005, 10:35 AM
Rented a snap cutter- $10.00 well spent. On my way to get the stainless covered coupler. Thanks for the advice!

06-16-2005, 08:03 PM
I installed the coupler but it just doesn't look right due to the different diameter of the two pipes. The OD of the cast iron is smaller than the PVC. I used the coupler with the solid stainless steel band. Do they make one that is smaller on one side to accommodate the difference? Should I have used the one with ridges in the stainless steel sleeve?


06-16-2005, 11:07 PM
If you have the older cast iron, 3.125" in diameter, you can use a mission coupling that is "copper" X "no-hub cast".
The copper side works well on the old cast, and the no-hub side will slip over the PVC.

06-22-2005, 06:31 PM
Thanks- got the coupler from a plumbing supply store. Fits like a glove.

As I move through my project I'm becoming more and more skeptical of the advice folks at the orange box give. This isn't the first time I was pointed to the wrong fitting.