Pour 1 gallon boiling water into the drain.
Plunge the drain vigorously for about 10 plunges.
Pour 1 cup baking soda into the drain, followed immediately with 1 cup white vinegar. Let the mixture foam and work down through the drain pipe for 30 minutes.
Pour 1 gallon more of boiling water down the drain.
Push a pipe snake into the drain if there is still blockage in your pipes. Push the snake down into the drain as far as possible, and push and pull slowly for about 10 seconds. Turn on your hot water supply for about 30 seconds and let the water flush any broken-up residue down the drain.