Step 1 – Put the DRY baking soda down the drain. I use about 3/4 of a cup. ( If you're having a hard time removing the sink stopper to put in you baking soda, click here to find out how to remove it correctly.)
Step 2 – Pour 1/2 cup of vinegar down the drain after the baking soda. Be sure to cover the drain immediately afterwards with a rag or plug, filling the hole completely so nothing can escape. This is because the interaction of the baking soda and vinegar will cause a “mini volcano” that will want to come up and out of the drain..you want to keep it down there to break up the clog.
Step 3 – Leave this concoction in the drain for about 30 minutes. While you are waiting, boil a tea kettle full of water.
Step 4 – After 30 minutes, remove the plug and slowly pour the HOT water down the drain.
Thats it... by now, all should flow smoothly. If not, just repeat the process 1-2 more times to break up the stubborn clog.