Is my sink trap leaking because it's missing a seal?

Question

I have absolutely no clue about plumbing so I apologize if any of the terms I use are wrong.

My p-trap is leaking, the outlet side threads on to the pipe in to the wall, but the inlet side just pushes up against the drain pipe from the sink. I thought this was maybe normal, but it leaks badly if there is even mildly heavy flow of water running through.

Looking at it, it looks like there used to be a seal glued on that maybe would have allowed it to screw on? I'm not actually sure. To be honest I just now realized that the rubber part was not actually a part of the p-trap.

So what happens now is the inlet side scootches up and down the drain freely, and leaks pretty badly. It seems like previously there was a rubber seal that was attached to the drain and the screw would then pull the p-trap up against the seal (but over time it just ripped it off).

Is there a better way to do things here? Should I get a new seal and just glue it back on? Any perspective is appreciated, thanks! Also happy to provide more info/photos.

EDIT for posterity: what I am referring to as the "seal" was a rubber slip joint washer that had totally disintegrated.

Answer 1

The two sides of the trap should use different kinds of washers. The left side in your picture correctly has a flat washer that gets compressed between the flanges of the two pipes that face one another. The right side of the trap is a "slip joint". It needs a different kind of washer that is missing. No glue! A slip joint washer is V-shaped in profile.

It slips tightly onto the inner pipe and then when you tighten the nut, the sharp end gets shoved and compressed between the two pipes forming the seal.

Take the trap with you to a hardware store to buy the correct size slip joint washer. If you can easily unscrew the tail piece from the sink, take that also and you can assemble the joint in the store to make sure you've got the right thing.

The dark metal flat washer in the third picture, on the right side of the trap, is probably supposed to help tighten the joint. Rubber washers on metal pipes can stick, and that ring should help the compression nut to turn without trying to turn the washer on the pipe. However it looks damaged, maybe rusty? So it will not do that job, it might do the opposite! Take that with you and try to replace it too, maybe with a teflon flat washer if you can find one.

Answer 2

The nut around the drain pipe that screws down from the top is called a compression nut. Yes, there should be a compression ring/gasket inside the nut that gets compressed when the nut is tightened preventing leaks. Any plumbing store or home store will have what you need.
The simplest way to get the correct part(s) is to take the old fittings with you when you go in. It's a simple fix requiring the only the right parts and an adjustable wrench - no glue necessary.