Boil 4–6 cups of water. Carefully pour the boiling water down the drain. This flushes away the dissolved debris.

Cover the drain opening with a rubber stopper or a damp cloth to contain the CO₂ pressure, forcing it down into the clog. Leave for 15–30 minutes.

Pour ½ cup of baking soda directly into the drain. Use a funnel if needed to ensure it reaches the pipe.

Immediately pour 1 cup of white vinegar into the drain. A vigorous fizzing reaction will begin.