Pour ½ cup of dry bicarbonate of soda directly into the drain. Try to get it past the drain strainer and into the pipe.

Pour a full kettle of boiling water directly down the drain. This softens any greasy or waxy buildup, making it easier for the next step to work.

Quickly cover the drain opening with a plug or a damp cloth. This traps the carbon dioxide gas inside the pipe, forcing it to push against the blockage rather than escaping upwards. Leave it for 15–30 minutes .

Immediately pour 1 cup of white vinegar down the drain. You will hear a vigorous fizzing sound—this is good.

Here is the science and the step-by-step method to unblock your sink using bicarbonate of soda and its essential partner, vinegar. On its own, bicarbonate of soda (a base) is a mild alkali that can dissolve some grease and dirt. However, its true power is unlocked when combined with a weak acid—specifically, distilled white vinegar.

A slow-draining sink is a universal frustration. Before you reach for a toxic, gel-based chemical cleaner or call an expensive plumber, there is a powerful, safe, and inexpensive solution already in your cupboard: bicarbonate of soda (baking soda).

While it won’t dissolve a solid metal hairpin or a lost earring, bicarbonate of soda is remarkably effective against the most common cause of sink blockages: . This includes grease, soap scum, food particles, and hair.