We use water all day long, despite the fact it can due immense damage to our homes. Bathrooms and kitchens are most vulnerable to moisture and water leaks. There are many ways to protect your home, from using waterproof building materials to caulking any cracks or holes, but an overflow drain is also an important flood prevention feature.

How an Overflow Drain Works

It is a hole or opening that, once water has reached a certain level, allows the excess to flow back to the drainpipe. This unique drain serves two purposes:

  • Prevents water from spilling out if the stopper is closed or the sink is left running. An overflow hole doesn’t offer much protection when a drain is clogged.
  • Allows air to enter piping through the overflow channel to increase the speed of drainage. If the opening is completely submerged, air can’t get in and water will drain more slowly.

There are two different types of overflow drains—those for sinks and those for tubs.

Sink Overflow

  • One or two holes near the rim of the sink basin.
  • An outlet hole at the bottom of the channel, just below the basin, where water flows into the drainpipe.
  • The overflow doesn’t get closed off by the sink stopper; it is always open.

*An overflow drain can’t handle rapidly flowing water. If your sink is currently filling, the amount of water the overflow channel drains won’t match the amount flowing out of the faucet.

Tub Overflow

  • Is located a few inches below the rim. Water can therefore rise high enough to cover most of a person’s body.
  • In a traditional overflow, a hole is cut into the tub from where excess water is delivered to the P-trap; the drain line passes outside the wall of the tub.
  • Designed more like a sink overflow, an integral overflow is an opening along the interior of the tub that diverts water through its walls and down the tub drain.

*In a bathtub overflow drain, the overflow connection and drain opening are farther apart. If a clog is near the tub drain opening, the overflow fitting can stop water from spilling over.

How Do I Maintain an Overflow Drain?

Overflow channels don’t often get cleaned. And they aren’t flushed out unless the sink or tub overflows. Debris can therefore build up at the bottom of the channel. This not only impedes flow when water levels get too high; it can also cause general drainage problems. Here are some methods you can use to manually clean an overflow:

  • Liquid Drain Cleaner: Mix plain water with chlorine bleach in a 50/50 solution. Using a container with a pour spout, pour the mixture down the overflow hole. Wait 10 minutes and then flush the channel with plain water.
  • Plastic Zip Ties: Insert the pointy end of a long plastic zip tie into the overflow opening. Move it up and down and side to side, as far as it will go, until you can feel the blockage loosen and break free.
  • Rubber Hose: Let the sink fill higher than the overflow opening. Once water starts to flow into the hole, place one end of a hose against it and blow through the other end (use a 7/8-inch dishwasher hose or something similar). Drain the sink and repeat until air blows without resistance.

Contact Express Plumbing Heating & Air

Our licensed plumbers are experienced with all aspects of bathroom plumbing, piping, and drain cleaning. If an overflow drain isn’t working, we can fix it right away. We have various tools and methods to repair residential and commercial drainage systems throughout the Treasure Valley. Call (208) 398-0309 today to request service.

Express Plumbing Heating & Air

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