Plumber came to kitchen to take care of my clogged drain after I failed to do it myself. Below the sink, he took off the trap that had what he called a 3" pipe attached to it. Well as he was trying to remove it, part of the thread broke off. it was old and rusted. Now, he told me to have it replace. His job did not call for replacing pipes and had me sign a waver for that. That's fine. Now what I want to know is how to go about getting that pipe. I'm sure its not ready made, or maybe I am wrong. I know it probably won't be available in a regular hardware store. He said to ask for a 3" pipe, threaded on both ends and 3" long. Isn't that what they call a 'coupler"?