Black sludge can easily build up in the drain of the bathroom sink from mold and mildew development, as well as toothpaste and other particles you rinse down the sink and thereby allow to accumulate in the drain pipe. A moderately easy process, cleaning away the black sludge will take care of the blockage and leave your sink draining properly.
To clear clogs in sink and tub drains, use a funnel to pour in 1/2 cup baking soda followed by 1 cup vinegar. When the foaming subsides, flush with hot tap water. Wait five minutes, and then flush again with cold water. Besides clearing blockages, this technique also washes away odor-causing bacteria. • To speed up a slow drain, pour in 1/2 cup salt followed by 2 cups boiling vinegar, then flush with hot and cold tap water.