If you’ve ever left your bathroom faucet running by accident, this small but clever feature in your sink’s basin has probably saved you from mopping up a soaked floor.
Although it often goes unnoticed, the extra hole in your sink’s bowl serves an essential purpose in keeping your bathroom functional and protecting it from flooding.
Keep reading to learn more.
While many people — and even some curious animals — might find creative uses for the holes along the upper wall of the basin, their true purpose is a vital safety function.
Since the late 1800s and early 1900s, sink designs have included overflow holes, an important addition that made plumbing systems more efficient and reduced the risk of water damage.
Throughout the 20th century, the size and placement of overflow holes became standard across most sinks and bathtubs. Even though some modern, minimalist sinks skip them for visual appeal, most bathroom and kitchen sinks made for regular use still include this essential feature.
Primary functions
This clever bit of engineering improves both the safety and practicality of your sink. The overflow hole serves two key purposes:
1. Managing water levels in the sink:
These holes redirect extra water before it spills over the edge. Once the water level reaches the overflow opening, it channels the excess through a separate drain that bypasses the sink stopper.
However, it’s worth noting that this system isn’t perfect. If your faucet is running at full force, the overflow may not keep up, and water can still spill out. That’s why it’s best to treat it as a helpful safeguard, not a substitute for turning off the tap. It’s an effective feature when combined with mindful water use.
2. Helping water drain faster:
Overflow holes also let air enter the drainpipe, balancing pressure and preventing suction that can slow drainage. When the main drain is covered by water, a vacuum effect can form, which slows down flow and creates air bubbles.
By allowing air in, the overflow hole helps water drain more smoothly and reduces the chance of clogs or sluggish drainage.
In simple terms, overflow holes improve the sink’s plumbing efficiency by promoting better airflow and smoother drainage.
Where does the water go?
According to The Spruce, a standard overflow system connects to a hidden channel running underneath the sink basin, which is why you can’t usually see it from above or below.
The overflow usually includes one or two small openings near the rim of the sink. When the water level rises too high, it flows into these openings and travels through the concealed channel to an outlet that connects with the main drain. Because the overflow operates separately from the sink stopper, it’s always open. This design ensures that any excess water is safely diverted into the drain instead of spilling over.
How to clean an overflow hole
Keeping the overflow hole clean is important for maintaining proper drainage and avoiding unpleasant smells. It also