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Do Bathroom Sinks Need an Overflow Drain? (Answered)

Certainly, you have noticed those extra holes in the bathroom sinks. No, we are not talking about the drain holes at the bottom of the sink, but the ones at the top of the basin rim.

These holes are the passage to the overflow of your bathroom sink. If you don’t have an overflow in your sink, could it be a problem?

Do bathroom sinks need an overflow drain?

Bathroom sinks don’t need to have an overflow drain. However, overflow drains are an optional fitting on your sink that improves the drainage system by creating a channel back to the drainpipe. As the name suggests, the purpose of an overflow pipe is to stop the basin from overflowing.

Are bathroom sink overflows required?

An overflow system in the bathroom sink is considered to be an optional fitting and it is not one that a bathroom sink cannot function without. But there is no denying that an overflow hole in your basin makes the water drain much faster.

 As you can understand, you would also prevent unnecessary flowing and spilling of water on the bathroom floor if you have an overflow installed in the bathroom sink.

Do all bathroom sinks have an overflow drain?

All bathroom sinks do not have an overflow drain. Since this is an optional fitting to have on your bathroom sink, many people will avoid the extra cost associated with buying and installing an overflow in the sink.

Many also want to avoid the bother of cleaning the overflow drain as not doing so can jam the drain system faster and create the opposite effect.

Bathroom sinks that are particularly large and have enough drain space, usually do not come with overflow drains. Having mentioned that, it is wise to have an overflow just to avoid water spills, in case your drain is clogged or closed with a stopper.

What is an overflow on the sink drain?

The overflow on the sink drain is one or two holes that are usually located on the rim of the sink or the wall of the basin. Starting from the holes, a connecting pipe creates a channel which is attached to the rest of the drain system.

The overflow of a drain is mainly included to stop water from overflowing from your sink. Remember the times when the drain is sealed, and you have kept your tap open?

The holes through which the excess water flows back into the pipes and the sink again is the overflow of the sink itself.

Furthermore, the overflow is also meant to improve the overall drainage system of your sink, making the water and air flow more fluent and faster.

Why do bathroom sinks not have overflows?

You must have noticed how not all bathroom sinks have an overflow. Of course, most of the bathroom sinks have holes that you might or might not notice from the top. If your bathroom sink was a previous laundry sink, it might not have an overflow.

Here are why few bathroom sinks do not have overflows:

Having an overflow is not necessary:

The reason you see overflow holes in every basin rim you come across is because an overflow has important functions for your sink.

However, you may want to keep in mind how an overflow is not necessary like a drain hole is. That is why many bathroom sinks do not have overflow and without it functions perfectly fine.

No doubt you would understand the importance of one if your sink drain hole is clogged or closed and water has overflowed through the sink. 

Similar to how kitchen or laundry sinks do not have overflows, some bathroom sinks also have drainage systems without overflows.

The bathroom sink is large or deep enough:

The overflow is there to help you keep your bathroom floor wet. You must be wondering why we are saying so.

That’s because when, for either too much water flow or drain blockage, the water in the sink rises up, it is the overflow that makes a passage for the excess water to flow in.

The same can be done if the sink is deep enough, or large enough. Just like deep kitchen sinks which can take up a lot of water before it flows up, larger bathroom sinks do not need or have an overflow with normal drainage flow.

Overflow increases cost:

Bathroom sinks might not have overflow or in other words, many people might not prefer bathroom sinks with overflow holes simply because of how expensive they can get.

Overflow is an extra bathroom sink fitting, and it certainly adds a significant amount of cost. Even if you are fitting a new bathroom sink with integrated overflow, it is likely that the plumbing costs will also increase just because it is additional work to install one.

To avoid this extra cost of bathroom fittings, as well as installation, bathroom sinks do not always come with an overflow.

The double basin is an advantage:

Many bathroom sinks, particularly in modern and more expensive homes and hotels do not have overflow holes. This is mainly because these bathrooms have double sinks.

Double sinks or larger sinks usually do not require overflow because these sinks successfully overcome the same problems as an overflow does.

When a bathroom sink has a double basin, when the water level rises in the main sink, the second sink usually acts as tailback support to take up the excess water.

Not everyone can install an overflow:

As we already mentioned how overflow is an extra fitting that comes with a cost.

Installing a bathroom sink with an overflow is expensive but what makes many prefer sinks without overflows is the hassle to install them. Yes, installing an overflow is hard work and without proper plumbing knowledge, you would not be able to install it.

How does bathroom sink overflow work?

The basic function of an overflow in a bathroom sink involves creating a channel from the sink to the bottom of the drain for excess water to flow when the sink is brimming.

The channel, which is also known as the overflow channel, makes sure that air enters and leaves the drain pipe faster. As a result, the excess water from the basin will go away much more quickly. Both the basin and the sink overflow pipe are connected to the drain point.

The only difference is that the holes on the overflow are never closed. They can be clogged, and hence the overflow needs regular cleaning.

The overflow works by making sure that the water on the basin does not spill down in all directions on your bathroom floor.

Other than that, overflows also improve the overall drain system. That is why you probably won’t see bubbles as water goes down the sink if there is an overflow in your bathroom sink.

This also means that water drains down the sink much faster because of the clear air passage.

How to install sink overflow drain?

To install a sink overflow, drain in the bathroom sink, you may follow the given steps:

Mark the rim:

Make a spot on the rim of the basin. Make sure the mark is at least an inch off the top of the rim.

Make a hole in the rim:

Now, you would be needing a saw to drill a hole into that spot. The hole should not be bigger than 1 inch in diameter.

Apply plumber putty:

Apply a generous amount of plumber’s putty to the bottom of the drain hole of the sink. Now, you can fit the overflow pipe into the putty and slide it through.

Seal the pipes:

Use a hose clamp to seal the drain points.

Clean the putty:

Finally, wipe clean the plumber’s putty of the pipe. And run the tap water to test the fitting.

Where does the bathroom sink overflow go?

The connection of the bathroom sink overflow starts from the rim of the basin.

The pipe goes from the overflow holes, creates a passage for air to flow from the bottom of the basin, and is finally attached to the drain hole itself.

Can you use an overflow drain in a bathroom sink without overflow?

Simply put, your bathroom sink can only have an overflow drain if it is equipped without an overflow.

Without the drain system of an overflow bathroom sink, the drainpipe connection will be completely altered, making it impossible to have an overflow drain.

Do bathroom sinks without overflows drain slower?

Bathroom sinks without overflows drain slower than ones that are equipped with overflows.

This is because, with an overflow, the drainage system is made much faster due to the uninterrupted flow of air.

This airflow is especially required for fast drainage if the drain hole is blocked.

Do bathroom sinks come with stoppers?

Generally, new bathroom sinks do come with stoppers as an extra fitting. Though, this is a completely optional fitting and not necessary when you are shopping for bathroom sinks.

Stoppers are more common in kitchen and tub skinks to be specific.

Final Thoughts:

Your bathroom sink will do just fine without an overflow drain. Nevertheless, if you want an extra pathway through which air passing becomes faster creating a better drainage system, you may want an overflow. Remember, overflow can be expensive and difficult to install in a bathroom sink.