How can I extend this waste drain for new bathroom sink?

Question

I'm looking to extend this pvc waste pipe coming out of the wall to accommodate my new bathroom sink. It's too short as it is and doesn't quite reach the new p-trap placement. Does anyone know how this is connected? Is it glued or cemented in? How do I remove and replace it with a longer piece and ensure I won't have a leak?

Appears like a galvanized steel connection in the wall.

UPDATE: I was able to twist and turn and get the drain pipe out far enough to make a decent connection (fully extended about 7.5" out). The pipe wasn't threaded, just jammed in there. Not sure how much of the pipe is left inside though, may be a concern.

Is it OK to use this extended pipe for my connection?

Do I need to glue or seal anything? Or should I take completely out and install a new pipe?

Answer 1

Caveat: I see now that your steel hub is very small, which is probably why things are set up as they are. My solution may not work. You may need to open the wall and enlarge the hub or replace a section of pipe with PVC and a sanitary tee.

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My guess is that you have a threaded pipe hub there, into which the plastic trap component has simply been inserted. If that's the case:

• Clean up the threads and extend with a threaded pipe nipple of the appropriate size, using thread compound as a sealant

• Add a female PVC adapter for 1-1/2" pipe

• Install a pipe stub and a slip-joint adapter

• Insert the outlet of your trap assembly into that fitting and snug up the compression nut

Answer 2

The part you show is not a pipe, it's a tailpiece - it SHOULD be going into a compression fitting that can be loosened to allow it to slide in or out, or to be pulled out and stuck into a tailpiece extension that would itself then go into the wall. But I don't see a nut, (or maybe I see half a nut?)

A tailpiece is "pipe shaped" but not the same size as pipes, and the fact that it elbows into a compression fitting outside the wall is diagnostic. There should be a similar (but perhaps galvanized) nut on the wall side. If so, remove that and slide it back on the tailpiece, then pull the tailpiece out. Add a tailpiece extension, unless you find that there's already sufficient tailpiece stuck into the pipe at wall to just slide the sealing ring (it's supposed to be an adjustable slip joint) and retighten the nut.

If you do get a tailpiece extension, know that it's common to have to trim tailpieces - they are sold long, and extensions are sold in a only a few lengths - when you have more than you need, you are expected to cut off the excess (don't overdo that, though) so it fits.

Incidentally, plastic tailpieces are more commonly polypropylene than PVC. There are, of course, also chrome-plated brass and stainless-steel tailpieces. The only ones I avoid like the plague are the accordion-pleated "flexible" ones, which are prone to clog and to break at rates far above normal "rigid" tailpieces.