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.

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 .