What is the Purpose of a Sink and Tub Overflow Drain?

What is an Overflow Drain?

An overflow is an opening that helps prevent flooding by rerouting excess water back to the drain pipe once it reaches a certain level. The design of an overflow differs between sinks and bathtubs.

48" Raksha Stainless Steel Japanese Soaking Tub with traditional overflow drain

How Does a Sink Overflow Drain Work?

The sink overflow drain is usually near the top of the basin where water is diverted to the main drain and prevents it from overfilling. The overflow drain typically bypasses the stopper and utilizes gravity to allow excess water to flow down the drain; however, they aren’t made to handle rapidly flowing water and an overflow is still possible if the volume is greater than what the drain can handle.

Additionally sink overflow drains allow the central drain to work faster and more efficiently. It provides greater air flow and reduces suction ensuring smoother drainage.

Water draining sink through the overflow

How Does a Bathtub Overflow Drain Work?

The tub overflow drain is usually a few inches below the rim to allow the water to rise to a level that submerges most of the bather's body while avoiding a potential water overflow.

Traditional Overflow

A hole is cut into the tub to accommodate a drain that installs on the inside and outside walls to collect excess water and send it down the tub drain to the P-trap.

Water draining a tub through the traditonal overflow
Extended Pop-Up Tub Drain with Daisy Wheel Overflow Drain
Extended Pop-Up Tub Drain with Daisy Wheel Overflow Drain
Extended Pop-Up Tub Drain with Standard Overflow Drain
Extended Pop-Up Tub Drain with Swivel Head & Overflow Drain
Extended Lift and Turn Drain with Daisy Wheel Overflow Drain
Extended Lift and Turn Drain with Daisy Wheel Overflow Drain

Integral Overflow

An integral overflow is designed similarly to a sink overflow. An opening is cut along the interior of the bathtub to divert extra water between the walls and send it down the tub drain. This is a valuable option for those not wanting exposed piping in their space since the overflow channel is built into the tub's inner wall.

Water draining a tub through the integral overflow
Toe Tap Tub Drain in Chrome for integral overflow drain
Toe Tap Tub Drain
Pop-Up Tub Drain with Hub Adapter for bathtubs overflow drain
Pop-Up Tub Drain with Hub Adapter
Lift & Turn Straight Tub Drain in Chrome for tub overflow drain
Lift & Turn Straight Tub Drain
Lift & Turn Tub Drain with Adapter Sleeve for tub overflow drain
Lift & Turn Tub Drain with Adapter Sleeve

There are different types of tub drains to guarantee a proper fit for particular bathtub styles.

Find out which one will work best for you in our tub drain buying guide.

Sink and Tub Overflow Benefits

  • It improves draining speed. The overflow allows air into the piping so your sink can remove water quickly.

  • These drains help prevent water damage from a potentially overflowing sink or bathtub.

  • Overflows reduce the amount of standing water in your sink or tub, therefore preventing mold or mildew while preserving water quality.

Extended Pop-Up Bathtub Overflow Drain, Gooseneck Tub-Wall-Mount Faucet and Hand Shower in Chrome
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