Can A Shower and Sink Share A Drain?

Are you planning to redesign your bath space? Or generally interested in learning how the plumbing system of a bathroom is designed. If that’s the case, like other people, you might be interested in knowing if a shower and sink can share the same drain.

The short answer to this is, Yes, a shower and sink can share the same drain. And it’s common in households to design the drainage system in such a way that both the sink and shower drain into the same pipes. This not only saves space but is also a cost-effective plumbing solution.

However, for the combo to work, there are some important factors that you need to take into account.  Further in this article, I will share those factors in detail. Then, we will go through the advantages and disadvantages of a combined drainage line.

Can Sink and Shower a Drain: Three Important Factors to Consider

The drain from the sink and the shower may be combined. However, when deciding whether to have your sink and shower share a drain, keep into account the following factors:

1.     Bathroom Layout

Bathroom layout is an important factor that determines if you can design a shared drain for sinks and showers. In normal circumstances, the layout allows you to attach both of these fixtures to the same drain.

However, in some bathroom layouts, there is a door in between the two fixtures, which makes it very hard for you to design a shared drainage system.

2.     Spacing between The Fixtures

Neither the shower should be far away from the sink, nor it should be very close to the sink. The appropriate distance, between the shower and sink, that the plumbers recommend for the installation of a common drain line is 5 feet. 

3.     Vent Placement

After you have fixed the space between the sink and shower, the next important thing is vent placement. The vent needs to be in between the two fixtures. The vent lets the bad odors escape the bath space and maintains the pressure in the lines. The good news here is that one vent is enough if the drain line is shared.

Advantages of Having a Shared Drain

Since you have looked at the factors you need to take into account when switching to a shared drainage line. Here’s a list of advantages a shared drain offers:

1.     Shared Drain Saves Space

First, if you have space constraints for your bathroom space, then the shared drain design is ideal for you. You just need to position the sink and shower at a distance of 5 feet from each other and connect them to a common drain.

With the common drainage of the two fixtures, fewer pipes, ducts, and vents will be used. That means a simple construction and less space usage.

2.     It is a cost-effective solution

If you would have used a separate drain pipe for each component, you would have needed two pipes.

However, if you share it, you will just need a single pipe for both the sink and shower. Consequently, the number of auxiliary attachments needed will also reduce. Hence, you get to save money a lot of dollars.

3.     Easy Repairing of Drains

If there is a separate drain line for each fixture, the plumbing design becomes complex; making the maintenance and repair hard. However, if the drain line is shared, the plumbing system becomes more organized and streamlined. You just have to check one line and vent, if the drain gets clogged.

Disadvantages of Having Shared Drain

It is possible to configure the sink and shower to share a drainage system. However, proper line design and planning would be required.

If it’s done incorrectly, you’ll soon run into issues that will be quite expensive to address. Here are a few problems you could encounter when you have a shared drain.

1.     The drains can backflow

A single pipe for multiple fixtures streamlines the plumbing system and is easy to maintain. However, when this line gets clogged, the drain blockage results in a backflow in all fixtures attached to it.

For instance, a blockage in the shared line due to sink hair will cause the shower drain to backflow; flooding the bathroom with sewage water.

2.     Blockage

Blockage of the drain line is also common when using a shared drain system. Since a single pipe is handling the wastewater of a pair of fixtures. So, the chance of blockage increases.

3.     You get to Hear a Gurgling Sound

If you already have a shared drain line between the sink and shower, you would have noticed a gurgling sound in the shower space when the water drains through the sink. This gurgling sound is annoying for most homeowners.

4.     Slow Drainage

Another downside of a common drain line is that water flows out slowly from the sink or shower due to the formation of Airlocks. As a result, the main pipe gets clogged with air bubbles, reducing the water reduce water flow.

You can solve this issue by installing adjustable air valves.  These valves automatically open and close when all of the air has been released from the pipe.


Before concluding this article, I would like to answer a few frequently asked questions related to shared shower & sink drains.

1.     Can Shower and Toilet share a drain?

Yes, a shower may share the drain with a toilet. For that, both of these fixtures need to have their own trap arms. However, this arrangement is not recommended since it often leads to sewer blockage and the spreading of smell into the bathroom. 

2.     What is the pipe sizing of the Shower and Sink Drain?

A shower drain is typically 2 inches in diameter. Whereas, the sink drain is usually 1.5 inches in diameter. If you choose a pipe of a smaller size, that will lead to blockages.

3.     Can the bathtub and sink share the same drain?

Yes, just as a shower can share a drain with a sink, a bathtub can also do the same with a sink. The rest conditions are the same.

Final Words

The showers and sinks can share a common drain. However, there are factors such as spacing, layout, and vent placement, which determine if the combination is possible.

A shared drain between any two fixtures is cost-effective and space-saving. Yet, there are some downsides to that. When you install a shared drain, there is a chance that the drain clogs, backflows, or water moves out slowly.

Keeping in view these main points, I hope that you can make an informed decision about whether you need a shared drain or not. 

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