Opening wye plug in older cast iron sewer pipe

[derry29]

My basement cast iron 5"? sewer line is probably more than 50 years old. In a 2-foot section, there is a wye of about 2" I.D. with a threaded plus with a square boss. I want to install a washing machine/utility sink drain line into this wye. Can I just unscrew the plug and find an adapter for a 2" copper drain pipe? Is there a danger in trying to unscrew something that old? How can I minimize the danger of breaking something? Thanks.

[PLUMBER RICK]

sometimes tightening first will break it loose. sometimes heat the plug a little bit. other times i use a hole saw to drill it out and pry out the remaining thread.

don't use brute force as something will give and it's usually not the plug:eek:

bigger problem is the drain for your laundry will still need to be vented.

rick.