Why Does a Bathtub Need a Second Hole in the Wall?

Probably everyone has noticed that, besides the drain at the bottom, every bathtub has another hole at the top. But not everyone knows what it’s for. Let’s clarify this. This component is humorously called an “overflow drain.” It is an essential part of any bathtub. It is a simple system designed to remove excess water from the bathtub and prevent overflow in case of careless water use.

The design includes two openings: one at the bottom of the bathtub and one on its rim. These are connected to each other and to the sewer system. In simple terms, the overflow drain is an additional hole, also connected to the drainage pipe, located at the upper part of the bathtub.

Through this hole, excess water is directed back to the sewer—say, if you suddenly decide to take a bath together. Another equally important function of this hole is to increase the speed at which water drains. As long as the overflow drain is not filled with water, it allows air to enter the pipeline.

Thanks to this, the bathtub’s drain hole will pull water out much faster than without an overflow system. Additionally, there are two ways to handle the water drainage for overflow drains.

1. Traditional Method: This method channels excess water out of the bathtub through a pipe installed on the outside of the bathtub. The water then moves through pipes to the siphon, which also receives water from the drain hole. This method is considered the most reliable for directing water to the sewer. It is important to ensure that the siphon does not become clogged.
2. Integral Method: This involves integrating the overflow channel into the internal wall of the bathtub through a special opening and leading it directly to the drain. This method eliminates the need for additional pipe fittings and siphon installation but carries the risk of the overflow drain not handling strong water flow.

The main advantage of the overflow drain is that it is always open. This prevents any mishaps related to clogs or a forgotten open faucet.

Overall, today’s plumbing market offers overflow drains in various designs and configurations. It’s up to you to choose one that fits your taste and budget.