Look up remedies for a clogged sink drain, and you'll find plenty of sites telling you to use baking soda and vinegar. Sometimes salt is included in that mix, but not always. You'll also find sites telling you that baking soda and vinegar cancel each other out and are useless. So, is this actually a good combination to try before resorting to calling a plumber? How do you get the combination to have any effect?
Slow Versus Clogged
First, whether or not this combination will work depends on just how "clogged" the sink really is. If the drain is merely slow, and you can get the water to drain out eventually, then you can try baking soda and vinegar as a way to open up the drain. But if the drain is clogged to the point where there is a bunch of water stuck in the sink, using baking soda and vinegar is generally impossible unless you can remove enough of the water to empty out the sink and part of the drain. The baking soda and vinegar have to be inside the drain and not above it for the combination to have any effect.
You Must Plug up the Drain Opening
Assuming you can get the baking soda and vinegar into the drain, below the opening, you have to be sure to plug up the drain opening after putting the two into the drain. When baking soda and vinegar meet, you get the fizzing action that reminds so many of the baking soda volcano models they used to build in elementary school. But that fizzing action won't do a thing if the bubbles can escape upward out of the drain. You need them to expand downward as the pressure created by the expanding bubbles is part of what works against the clog in the drain. If possible, plug up the overflow hole as well. Kitchen sinks won't have it, but bathroom sinks will.
Don't Leave It Overnight!
Sometimes you find advice to put baking soda and vinegar down the drain and then leave them there for several hours or overnight. Don't do that. First of all, if the combination is going to work, it's going to work within an hour or so, and most likely much faster than that. (If it doesn't work at all, then you may have a clog that you need to call a plumber for.) Letting it sit would just waste time. Plus, if you let it sit for too long, the baking soda can actually start to harden and make the clog worse. That stuff doesn't always just disappear in water.
If the baking soda and vinegar don't work, or if the sink is too full of water for you to use the combination, call a plumber. If it's after hours, call anyway and have their on-call emergency plumber come by. You need that sink drain to be open, and a plumber can take care of the job very quickly.
For more information, contact a local emergency plumber.