1. Since it's the drain, there is no need to turn off the water anywhere.
2. You need to unscrew the nuts that are holding the white plastic drain together: the one where it meets the brass tube, the next one, and possible the third one. You should be able to do this by hand. If they are on too tight to do by hand, use a slipjoint pliers very carefully and make sure you are unscrewing the nuts...not tightening them.
3. Have a pan under the plastic pipes as the small amount of water that is sitting in the gooseneck will spill out.
4. Inspect the pipes that you have taken apart for gunk.
5. If there is no obstruction in the plastic pipes, the problem may be a hair ball that is trapped near the drain. There is a way to remove the stopper. If you look at the back of the brass pipe, there is probably a nut on the backside that a drain lever goes through. You will need to remove that nut to extract the lever, and then you can remove the drain plug to check.

If these things don't work, re-post.

If you think you may have a hair plug, you can do step 5 of my instructions first, and then 1-4 if that doesn't work.

Thanks very much, Kudzu! I'm at work now, but I'll give this a try tomorrow. I'll report back.

Before you take anything apart. Go to HD and buy a $2.00 zip strip. Force it down the sink drain and pull it out. This will remove the hair.

Thanks for the suggestion, Tim. The zip strip is something that can go down the drain even when the stopper is in place?

alisande-
A zip strip can work with the stopper in place. It's basically a plastic strip with little teeth that can grab hair. Sometimes they work well, sometimes they don't. It depends on the nature of the clog. At least you have all the info you need to clear most any clog...unless it's much further down the drain line, in which case you'll need to run a snake. Good luck. Please report back on what you find.

Okay, I'm back with my report. I wasn't able to get to Home Depot or under the sink until today, and by this time I had standing water in the sink unless I jiggled the stopper. This led me to believe the blockage wasn't very far down, so I figured I'd start with the zip strip.

I followed the directions, pushing it all the way down and pulling it back up slowly. It emerged with the teeth covered in something black. I was expecting to see hair, but not a hair in sight. The water now drains out quickly.

Any idea what this black stuff is? It didn't smell, at least not that I noticed. I'm sure there must be more in the pipes. Would it hurt the pipes if I poured straight chlorine bleach down the drain? Or perhaps you have a better suggestion?

Thanks so much for the help.

Susan

"It emerged with the teeth covered in something black."

Most likely rotting hair, soap residue,grease, and any one of a number of other things that runs down the drain.

The strips can help clear the line, but it really sounds like a dis-assembly and thorough cleaning is in order.

Some of the newer chines drain assemblies do not have a way to remove the stopper without first removing the actuator arm, and the arm passe almost all the way across the drain maximizing catching waste.

Most older equipment had a rotate and lift out set of cuts in the side of the stopper and the actuator did not go al the way across the drain to catch stuff.

You have to keep in mind that the pressure in a drain is very low (only as deep as the standing water).