Installing a bathroom sink. I have a tailpiece/downspout that I'm attempting to connect to a p-trap, and then subsequently connect the p-trap to the drain sticking out of the wall:

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The p-trap I have is here:

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Part C screws onto the thread of the drain (sticking out of the wall) perfectly fine. But part A is exactly the same size as the inside dimension of the same drain, and so it just butts up against the the drain with no way to secure the p-trap to the drain.

Furthermore, the tapiece fits into part E just fine, and I can screw E onto the threads, but I am still able to easily pull part E of the tailpiece., so I'm not sure how I'm supposed to affix it to the tailpiece securely. Any ideas?

  • 2
    The trap parts look like a kit. What size are they? (1-1/2" or 1-1/4"?) I'm wondering whether your tailpiece and trap kit are 1-1/2 while the wall fitting is for 1-1/4. The nut (part C in your photo) has the same thread pitch and size for both, so the fact that the nut fits the wall drain doesn't tell us much.
    – Greg Hill
    Sep 19, 2022 at 23:31

1 Answer 1


Regarding the tailpiece, it is a "compression" connection. Remove nut E, slide it up the tailpiece, then slide a flexible rubber compression washer (F?) over the tailpiece end. Fit the tailpiece end into the trap tube - the washer should jam up against the end of the trap tube. Then slide the plastic nut E down, tighten it on the trap tube threads, and it will compress that rubber washer, squeezing it around the tailpiece and making a secure waterproof connection.

Along with a smaller pipe to fit into the wall, you'll need another (red rubber) compression washer for the connection at C. Inner diameter of the compression washer should match the outside diameter of you new smaller pipe.

  • The red rubber washer is often white/clear plastic of some sort and those work just as well. I think they started making rubber ones because DIYers think that a washer must be rubber and were asking 10000 questions about the plastic ones, but don't think twice about buying a rubber one.
    – FreeMan
    Sep 20, 2022 at 12:05
  • @FreeMan I've had problems with some non-rubber ones that were not as flexible as rubber. You're right that white rubber or other equally flexible material is fine.
    – Armand
    Sep 20, 2022 at 18:31

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