The overflow drain in your sink is a small, often overlooked feature that plays a critical role in home maintenance and safety. While most people don't think about it until a clog occurs, understanding how this system works can save you from expensive water damage and unpleasant bathroom odors. What is a Sink Overflow Drain?
Pouring boiling water directly into the overflow hole (using a funnel) can dissolve soap scum and minor blockages. Warning: This is not recommended for glass or fragile ceramic sinks due to thermal shock.
At its core, the overflow drain is a passive hydraulic bypass.