What is an Overflow Drain?

Malcolm Tatum
Malcolm Tatum

Overflow drains are secondary drains that work in tandem with primary drains to prevent an overflow or spillage of liquid out of some type of receptacle. Their main function is to ensure that damage is not caused to the area surrounding the receptacle as a result of the liquid reaching the rim of the container and flowing into the area unchecked. These drains are often located an equitable distance from the lip or rim, but still significantly higher than the primary drain located at the bottom of the receptacle.


A classic example of an overflow drain is found in many homes. Most bathroom tubs and sinks are equipped with this secondary drain as a means of preventing water from spilling onto the surrounding floor and causing water damage. With the tub, the overflow drain is often located several inches below the tub rim and helps to minimize the chances of the tub overflowing while a bath is being drawn.

In like manner, an overflow drain is also found in the bathroom sink. As with the bathtub, the presence of this secondary drain in the sink helps to prevent the basin from filling completely and possibly overflowing onto the surrounding floor. This simple design element can mean that the chances of water damage to the flooring and possibly baseboards in the room are significantly lower.

An overflow drain is also used in manufacturing plants and other commercial assembly operations. The drain may be used to redirect water after it reaches a certain level, or serve as a means of effectively maintaining a certain level of any type of liquid in place as part of the manufacturing process. In both domestic and commercial applications, the overflow drain is coupled with overflow plumbing or tubing that makes it possible to route the excess liquid safely away from the receptacle.

As with any type of drain, there is always the possibility of an overflow drain becoming clogged. When this occurs, it is usually a good idea to call in a plumber. A plumbing professional will be able to accurately evaluate the type of plumbing or tubing used in the construction of the drain and remove the blockage using methods that will not damage the secondary draining channel.

Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including wiseGEEK, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

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Discussion Comments


My landlord has told me that the reason for the water damage under my bath tub is because I had taped the overflow drain so it would drain water. Does this make sense? I thought the only purpose of the overflow was to make sure water doesn't spill onto the floor. If I had it taped, how could that have created water damage when I made sure water never spilled onto the floor? It seems to me the damage would be cause from old leaky pipes and the running of water from shower from both my shower and the two people who live in the apartment above me (I live alone and only have overnight guests two or three nights a year).


I too have come to loathe the overflow drain on any bathtub I come across. There is just something I find perversely annoying about someone reached from the past into the future to prevent me from enjoying a relaxing soak in a tub full of water. The continuous gurgle of water falling down a cast iron pipe is enough to ruin any good atmosphere.

If I cannot find a proper way to banish the overflow drain from my life I may just have to import an ofuro.


How would I fix or repair an overflow drain tube that has rusted through? I live in a really old house, and was getting the worst leaks from under my sink. I had no idea what was going on until I finally figured out that it was actually the overflow drain that was leaking instead of the regular drain.

Now I'm kind of stuck because the sink is so old that I'm pretty sure they don't make that specific part for my specific sink anymore, and I'm not sure how I would go about finding a replacement.

Do any of you home-repair types have any advice for me?


What would be the benefits of using a drain with no overflow as opposed to a drain and overflow set up? I mean, aside from the obvious advantage of the overflow taking any extra water, but what would be some of the other pros and cons?

I am thinking about refurbishing my bathroom, and I had no idea what I was getting into with the whole sink/fittings issue. Now I'm bombarded with all these advertisements for sink drains without overflows, sink drains with overflows, and sink drains with optional overflows.

What on earth is the difference between these things, and why would I need one on my bathroom?


I may be crazy, but I've always hated bath tub overflow drains. The one in my childhood house must have been designed by someone who never, ever took a bath, because it was located about seven inches above the bottom of the tub, so you could never take a proper bath.

I usually ended up just plugging the overflow drain with a washcloth to get a proper bath for a few minutes before it would stop working.

Now I hear that they actually sell overflow drain covers, which would have been infinitely more useful -- if I'm ever stuck with a bathtub like that again, I will definitely be hitting up my local plumbing store drain section.

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