Draining a Washing Machine into a Cast Iron Sewer Pipe

You need a hole saw to make the proper sized hole. You can buy a saddle that fits over the pipe to make the connection for the washer hose to go into.

Don't forget the trap and be sure the venting works. You may need a Studer Vent. Two issues. You don't want the retreating water to pull the water out of your trap and you don't want the washer hose siphoning sewer water back into the washer.

Air admittance valves such as the Studer have limitations on their locations. It's definitely worth investigating, though, and good points about the trap and venting issues.

I think it would be simpler to just cut a few inches of pipe out, and install the correct fitting using no-hub connectors.

Actually, I decided to have a plumber do it for me at the same time he was installing a new water heater for me and that's how he did it. The height of the drain tube did worry me a little bit since it's at least a couple of feet above the top of the washer, but it does seem to work just fine.