My bathtub won't drain

Take a wire coat hanger. Bend the hanger straight and use the end that doesn't have the hook. Slide the hanger down the over flow to see if you have a piece of your trip lever down there.

That tube is usually hollow. When draining, is is pulled high enough to uncover a hole in the side of the drain. WHen sealing, is slides down, covering the hole.

drain

It is hollow so the water can flow through it from the overflow when the tub is overfilled.

As far as your drain goes,Cover the overflow with a wet washcloth or seal it however you can so it stays airtight then begin with the plunger.If the water freely bobs up and down it is clogged beyond where the drain ties into the vent and it would then be time to dial your favorite drain person!Good luck.

It is also common for a wad of hair to accumulate in the "shoe" of the drain, catching on the cross in the strainer. This is between the chrome thingie in the tub and the tee part of the drain where the bucket lines up. If there is a chrome cover with a screw, remove that. Needle nose pliers are good for pulling out the hair clog.

Aside from that, it's also possible that the drain below is plugged.

And a third possibility is that the drain is out of adjustment and the bucket is too low to open enough. They can go out of adjustment. (Most of them, anyway.)

As a father of two daughters with long hair, I have to take the drain plug out (popup style) periodically and pull the mass of hair out of it. This past time it looked like I pulled out a squirrel from that thing. Yuck!