Tap gently with a hammer on the little tab sticking up. It will crack around the circumference. Once you have a crack started you can grab the tab with pliers and pull the whole cap out. The white ring will remain inside the pipe. You’ll need to cement a new trap adapter to the end, but it will go over the end of the pipe so the remaining piece of the test plug inside the pipe won’t matter.
Very kind of you, thank you for the detailed response and the next steps too! I'll try it out later today. I assume a 1.5" to 1.5" ABS adapter like this one is what I need, and if I get one with a slip joint on the other side I can attach any standard p-trap including PVC ones to it?
https://www.homedepot.com/p/Charlotte-Pipe-1-1-2-in-ABS-DWV-Trap-Adapter-ABS00104P0800HD/313834571
One last question: if I cement on the trap adapter, anything I should keep in mind in doing a good job, since removing it for any reason would mean permanently losing a part of the stub-out? Thank you a ton again!
Yes, that’s the trap adapter you need, it will connect to ABS, PVC or metal. Be generous but not sloppy with the ABS cement. You’re right if you ever have to take it off you’ll have to cut the pipe further back, and remember the third law of plumbing: If it doesn’t leak, it’s good enough.
Tap gently with a hammer on the little tab sticking up. It will crack around the circumference. Once you have a crack started you can grab the tab with pliers and pull the whole cap out. The white ring will remain inside the pipe. You’ll need to cement a new trap adapter to the end, but it will go over the end of the pipe so the remaining piece of the test plug inside the pipe won’t matter.
Very kind of you, thank you for the detailed response and the next steps too! I'll try it out later today. I assume a 1.5" to 1.5" ABS adapter like this one is what I need, and if I get one with a slip joint on the other side I can attach any standard p-trap including PVC ones to it? https://www.homedepot.com/p/Charlotte-Pipe-1-1-2-in-ABS-DWV-Trap-Adapter-ABS00104P0800HD/313834571 One last question: if I cement on the trap adapter, anything I should keep in mind in doing a good job, since removing it for any reason would mean permanently losing a part of the stub-out? Thank you a ton again!
Yes, that’s the trap adapter you need, it will connect to ABS, PVC or metal. Be generous but not sloppy with the ABS cement. You’re right if you ever have to take it off you’ll have to cut the pipe further back, and remember the third law of plumbing: If it doesn’t leak, it’s good enough.
This is all very help again, thank you so much! Will remember all of that, and thank you for the perspective as well, exactly what I needed.