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The Purpose of a Sink and Tub Overflow

 

 

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:

 

 Sink Overflow

 
The overflow in a bathroom sink serves two purposes:
 
  1 – It diverts rising water back to the drain pipe. This helps prevent water from spilling onto your counter or floor, which could result in water damage. While effective, sink overflows are not designed to handle rapidly flowing water. Water will still be rerouted to the drain, but the amount being evacuated likely won't be able to match the quantity filling the basin, so it is recommended to always be present when using your faucet.  
     
  2 – It improves draining speed. The overflow allows air into the piping so your sink can remove water quickly.  
     
 
 

 Tub Overflow

 
 Tub overflows are located a few inches below the rim to allow the water to rise to a level that submerges the majority of the bather's body. There are two types of overflows:
 
  1 – 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. 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.  
     
  2 – Integral Overflow: An integral overflow is designed very much like 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.