The small opening near the top of a bathroom sink is called an overflow hole. Although it may look unnecessary, it serves as a backup drainage passage when the sink begins filling too high.
If the tap is accidentally left running while the drain is closed or blocked, water enters the overflow opening before reaching the rim. A hidden channel inside the basin directs that water into the main drainpipe. This can slow the rising water and may help prevent the sink from overflowing onto the floor.
However, the hole is not guaranteed to stop every flood. A fully opened tap may release water faster than the overflow channel can drain it, especially if the passage is dirty or clogged. It is still important to turn off taps and never rely entirely on this feature.
The opening also allows air into the drainage system, which can help water leave the basin more smoothly. Over time, soap residue, toothpaste and grime may collect inside the channel and create unpleasant smells.
To clean it, use a small brush or pipe cleaner with warm, soapy water. Avoid forcing sharp objects inside or mixing powerful cleaning chemicals.
That tiny hole is not decorative—it is a practical safety feature designed to reduce spills and improve drainage.
