Can A Toilet and Shower Share the Same Drain? (Answered!)

For most of us, nothing is more mysterious than the pipes that run in our houses. We cannot understand how the toilet and the shower drain work, let alone their connections. So, can a toilet and shower share the same drain?

A toilet and shower can share the same drain if you first fit a common vent to prevent backflow and connect the two drains correctly using quality PVC connectors. Additionally, the connection should be within a 6 feet radius.

So, it’s generally not impossible to combine the toilet and shower drain. After all, their wastewater ends in one place (the sewer or septic tank).

I will share how you can properly combine the two drains to avoid serious leakage in your house. I will also discuss several other relatable questions that you might be having.

Is The Toilet and Shower Drain the Same

Can A Toilet and Shower Share the Same Drain? If Yes, How?

Overall, the toilet and the shower can share a drain, but you have to meet these three conditions:

1st Condition: Install a Common Vent

The primary issue with combining different drains is that their incompatibility can lead to an airlock, which encourages backflow.

In the case of the toilet and shower drains, the backflow features human waste and other filth, which could mess up your house or encourage a waterborne infection like cholera.

However, the issue is preventable by installing a common vent that allows wastewater from both drains to flow out without forming an airlock. In the long run, that prevents backflow.  

So, the first condition for the toilet and shower to share the same drain is installing a common vent, and I recommend the Oatey 39012 1.5 In NPT ABS In-Line Vent.

This spring-loaded ABS vent will prevent sewage backflow and is generally compatible with most drains.

2nd Condition: Use PVC Connectors

While a common vent is a must-install if you want to combine toilet and shower drains, it’s not the only condition.

Remember that toilet drain is typically larger than shower drain, and that makes them almost incompatible.

You can, however, ensure that the two fit perfectly by fitting suitable PVC connectors. The connectors usually are 2-3 inches in diameter.

Remember, you’ll have to cut the ends of the toilet and sink vents before connecting them. And since the sink vent empties into the toilet vent (the larger of the two), you’ll need to install sink traps to prevent wastewater or sewer gas from escaping into your house.

3rd Condition:

The last condition is that you should ensure you make the connection within a 6 feet radius.

If you connect the toilet and the shower not far from the toilet by more than 6 feet, the valve won’t feed the drainpipe correctly. If that’s not the case, then you should separate the two drains to avoid any issues.

Are Shower and Toilet Pipes Connected

The Supplies for Fitting Shower and Toilet On Same Drain

It’s essential that you double-check to ensure you’ve all the supplies you need to combine the toilet and shower drains. That includes the following:

  • Common vent
  • 3-inch PVC pipes
  • 3-inch PVC caps
  • Regular PVC connectors
  • PVC adhesives
  • PVC saw
  • Shower strap
  • 3-inch PVC bends

The other consideration is that you position the pipes and shower traps correctly (that’s higher than the position of your toilet). That’ll ensure all connections are airtight to avoid potential backflow. In case of a longer distance, you may have to install another vent.

Simple Steps for Combining the Shower and Toilet On Same Drain)

Generally, here are five steps for unifying the toilet and shower drains:

Step 1 – Preparation 

Prepare your supplies and then remove the flowing material or wall panels to access your piping.

Step 2 – Common vent installation

Add a common vent into your bathroom system to reduce backflow. The common vent should be about 5 feet from the toilet shower trap.

Step 3 – Shower-to-vent-connection

Now, connect your shower pipe to the common vent using PVC pipes and adhesive. While at it, ensure the shower pipes and s-straps are higher than the toilet.

Step 4 – Vent-to-toilet connection

Use the PVC connectors and adhesives to connect the common vent to your toilet’s piping.

Step 5 – Cure

Allow the adhesive some time to cure before testing the new drain.

Step 6 – Testing 

Once you connect everything, it’s advisable to flush the toilet and open the shower separately to ensure no leakages.

Is The Toilet and Shower Drain the Same

Are Shower and Toilet Pipes Connected?

Under normal conditions, the shower and toilet pipes drain at one place (the sewer or septic tank). So, that’s the area where the two are connected.

Remember, the toilet system contains two parts; the bowl and the tank. The bowl generally holds the wastewater after flushing and connects to the main drain, which leads to the sewer or septic.

On the other hand, the tank holds the flushing water (which is fed by the same line as the shower). So, the shower and the toilet pipes have the same origin (water source) and end to the septic or sewer.

Is The Toilet and Shower Drain the Same?

The toilet and shower drain are not the same. The only thing they have in common is that they are fed by the same water source and drain their wastewater in the same place (septic or sewer).

However, it’s now possible to combine the two drains as one, which you can do with PVC pipes, PVC adhesives, s-straps, and common vents. Once you combine the two, their wastewater will combine before getting to the sewer or septic tank.

Can I Fit My Shower in an Existing Toilet Drain?

Given that all the drains (shower, sink, and toilet) empty all their wastewater in the same place and have the same water source, it’s possible to swap them. So, yes, you can fit your shower in an old toilet drain.

Why Connect the Shower and Toilet Drain?

So, why go through all the stress of unifying your shower and toilet drains? Well, here are two key reasons:

  • Cost-Saving 

By joining the shower and toilet drains, you save on plumbing costs. In that case, you don’t have to buy lots of fixtures for the shower and toilet drain.

You also save on labor since you don’t need to hire a plumber to join as it’s all DIY. If you opt to install the drains separately, you’ll need more than one person to do the job, and that can be expensive.

  • Simplicity 

By combining the shower and toilet drains, you avoid complicated networks, often costly to maintain. The unification guarantees a much simpler but practical drain system.

Do Shower and Toilet Use Same Drain


1. Can Two Toilets Share the Same Drain?

It’s common to find more than one toilet in rentals, hotels, and homes, and they mostly share the same drain. The only issue is that they need different stacks if the toilets are on opposite sides instead of the same side where they can share a stack.

2. Can Two Showers Share the Same Drain?

In most communal houses and rentals, showers share the same drain. So, it’s not a problem. They, however, have to empty into a pipe that’s large enough to bear the combined floor. If not, water will flow back and flow out through one of them.

3. Can A Shower Share the Same Drain?

Since the shower and toilet empty their wastewater at the same place, they can share a drain. However, it is essential that you prevent backflow by fitting a common vent and ensuring that the two drains form a leak-free union.

4. Do Shower and Toilet Use Same Drain?

All showers and toilet wastewater end up in one place (sewer/septic tank). It, however, does not mean that all showers and toilets use the same drain. That’s unless you unify them, which you can do by installing a common vent and using PVC connectors and adhesives. 

5. Can A Sink and Shower Share the Same Drain?

The kitchen or bathroom sink can comfortably share the same drain with the shower. The secret is to connect them correctly to prevent leakage and use an effective common vent to prevent backflow. 

6. Is The Sink Connected to The Toilet Drain?

The sink and the toilet all empty their content into the sewer line or septic tank. However, some homeowners prefer to cut installation costs by connecting the sink drain to the toilet drain. That’s possible with using the correct pipes and installing an effective common vent. 

7. Can The Toilet and The Sink Share a Vent?

Not all vents work on toilet sinks but only common vents. So, before you can start connecting the toilet drain to the sink drain, ensure that what you have is a common vent. It’ll form the perfect union between the two and prevent wastewater backflow. 

8. What Happens When One Poops in The Shower?

If there is enough velocity and the p-strap is low quality or made of thin ABS, the poo may pass through your shower. So, it’s never a good idea to poop in the shower. Besides, you could end up blocking the shower. 

Can A Toilet and Shower Share the Same Drain? Closing Thought:

Now you know what it takes for the shower and toilet to share a drain. So, if you want to go this route for cost-saving or simplicity reasons, ensure you meet the conditions. Note that this project can be too technical. So, if you cannot do it, talk to an expert plumber nearest to you. 


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