This small hole is connected to the drainage pipe below. During use, there are many instances when users forget to turn off the faucet (for example, leaving to answer a phone call while waiting for the sink to fill). In such cases, once the water level reaches two-thirds of the sink, it will drain through the hole into the pipe, preventing water from overflowing onto the floor and flooding the bathroom.
While beneficial, this overflow hole can also cause users some inconvenience. Since it is located in a somewhat awkward spot, it can easily accumulate bacteria and mold, leading to unpleasant odors rising from the pipes.
So, if you notice an unpleasant smell in the bathroom, especially coming from this small hole, you can mix vinegar with baking soda and place the mixture into the hole of the sink.
The chemical reaction will help remove the dirt from the pipes within 5 to 10 minutes. Finally, flush the sink with warm water to complete the cleaning process. This method will ensure your bathroom remains fresh and clean.