Although the overflow hole can help protect the bathroom, it should not be treated as a guarantee against flooding. The opening is relatively small and may not always remove water as quickly as a fully opened faucet supplies it.
If the faucet is running at a high rate, the water may continue rising even after it begins entering the overflow passage. The hidden channel may slow the increase, but the basin can still overflow if the situation continues for long enough.
The protection may also be reduced when the overflow channel contains dirt, soap residue, mold, or other buildup. A partially blocked passage cannot redirect water as efficiently as a clean one.
For this reason, the feature should be viewed as a useful backup rather than a replacement for turning off the faucet. Paying attention while filling the sink remains the most reliable way to prevent accidental water damage.
Why the Small Opening Can Develop an Odor
