Just moved into a new house and had a new washer and dryer delivered today. When they installed them, they said they couldn't complete the washer install due to this cap on the drainage pipe.
They mentioned it might be a knockout, but, in trying to knock it out, all that's happened is my knocking out a chunk of it. I then decided to drill a hole in it and see if I could pull it out with pliers, which didn't work.
So, what is it, and how should I go about getting through it for the drainage line?