Can A Toilet And Shower Share The Same Drain?

A toilet and a shower can share the same drain with no problems. While this is true, they shouldn’t share the same waste trap arm. Careful consideration should be made during installation to prevent any problems. 

When you are about to make renovations to your bathroom, you might be tempted to try and use the same drain for both your toilet and the shower. Whether they can share the same drain or not is an important question and one that has a complex answer.

Everything in the drains will find its way to the main sewer line in almost all residential properties. Based on this fact, the shower and the toilet can definitely have one drain but this is not the case when it comes to sharing the same waste trap arm.

Here we’ll take a look at why they can use the same drain but also why it would be a bad idea if it’s not installed correctly.

can a toilet and shower share the same drain

How Do Toilet And Shower Drains Work?

Whether they are separated or connected to the same drain, both fixtures will eventually connect with the main sewer pipe. This makes it possible for them to share the same drain as the end location is the same. 

However, the fixtures don’t have the same type of waste. This is due to the difference between black water and greywater. Blackwater is any waste that includes urine or fecal matter. Greywater is generally from sinks and showers. 

It’s important that the two have separate waste traps for this reason. When you flush the toilet, water from the tank drops, forcing waste to leave the drain. Then, the drain should pass the waste to the main sewer system.

You want to avoid any chance of this backing up into your greywater pipes. 

Black and Greywater Definitions

Both of them fall under the category of “wastewater,” but there is a huge difference in their components and sources.

For instance, greywater is what comes from kitchen fixtures and bathroom appliances such as washing machines, sinks, tubs, and showers. It is not pure water, but it is not as contaminated as blackwater.

This makes it easier to process as the contamination in greywater usually comes from soaps, detergents, and shampoos. This is why it would be possible for two greywater sources, such as a washing machine and a sink, to use the same waste trap. 

As for blackwater, this is the wastewater coming from toilets. It is also used to describe the water from urinals. Blackwater contains high levels of contamination as it carries feces and urine.

This is why you want to avoid any chance of this material, or smell, backing up into the greywater pipes. 

Why Is It a Good Idea To Have a Single Drain for a Shower and Toilet?

a Single Drain for a Shower and Toilet

There are different building codes in different areas regulating the sizes of plumbing pipes and other plumbing matters. But, in general, it is okay to connect a shower and a toilet to the same drain. Here are some of its advantages:

A cost-efficient solution 

Ideally, you would have a separate drain line for each fixture or appliance in your home but you would have to pay a fortune for this to happen. So, when you connect both fixtures, the toilet and the shower, to the same drain, you are saving some extra cash.

Typically, buying and installing two sets of drains is more expensive than just one.

A more convenient way that works with a single stack system 

The idea of a single-stack plumbing system has long been seen as an efficient way of clearing water from your system. This system simply uses one main vertical pipe to dispose of all types of waste coming from a house.

This means all fixtures in a bathroom or kitchen are eventually connected to this main pipe, which leads the waste to the central sewerage line. Combining a shower and a toilet into the same drain works just fine with this popular system.

Choosing a separate drain line for every single fixture in your bathroom and kitchen can be a nightmare.

You will have to find a proper way for each separate pipe to fit into your building’s structure, which can lead to a very occupied pipe network. So, imagine the time, effort, and cost required for that kind of work.

Can a Toilet and a Shower Share a Vent? 

Well, this is a core issue when it comes to sharing the drain. Both fixtures need to be connected to a common vent. This common vent is a practical and cost-efficient way to vent a couple of bathroom or kitchen fixtures through the same vent pipe.

You can position the common vent between the toilet and the shower. The estimated distance between the vent and both fixtures should be 5 feet. If you fail to position the vent at this distance, you will need to add another vent.

If you are unsure about your ability to perform the wet vent process, you can consult with a professional plumber to avoid mistakes and damage.

If the vent is not installed and connected to the fixtures properly, you could end up with wastewater from the toilet under your feet while showering.

What Happens After Installing The Common Vent?

After the installation, you need to connect the vent to the shower, and then it is the toilet’s turn. It is important to work in this order. Don’t forget to keep your water supply off until you are completely done.

It is also important to keep the pipes of the shower at a higher level than the toilet’s pipping. Shower pipes need to have a slope of 1/4 inch per foot. This way, you will maintain excellent water flow and discharge when you are using the shower.

When you head to the toilet’s pipes to make the same connection, ensure that your toilet has a pipe that is 3 inches in diameter. This is larger than the pipes in the shower but for a good reason.

The amount of waste discharged from a toilet bowl is much more congested when compared to the amount of waste discharged from a shower.

Once the connection is made, you can turn the water supply back on to perform a test. Turn on your shower and flush the toilet to ensure the connection is working fine without leaks. If so, you can install the new floor tiles and enjoy your new drainage system.

What To Do If Either Drain Is Clogged

If everything is done properly, there should be no problem. However, it is not uncommon to face a clogging issue every once in a while, even with a professionally installed drainage system. 

using a plunger in the toilet

The most obvious indication of a clog is when you find water overflowing after flushing. To eliminate clogging, you can use the following methods:


Since clogging may be in the toilet bowl itself, it is better to try a plunger to clear the clog. If you are going to use a plunger, you will need one with a protruding bottom. This is the right type for unclogging toilets.

It is designed to provide the necessary water pressure required to get rid of the clog.

Drain snakes 

If the source of the clogging was the drain, you can use a drain snake. You can get this tool from a nearby relevant hardware shop or online.

  • Start by removing the cover of the drain
  • Push the snake into the opening
  • Keep pushing till the snake finds the clogging source. The clogging won’t let the snake go down any further
  • Use pressure and strength to twist the snake and repeat the action till you feel the clogging is cleared
  • At this moment, you can retrieve the snake, which will have debris from the clog. It is time to throw them in your trash can or in a plastic bag
  • Pour some water to guarantee there is nothing left in the drain from the clog

Drain cleaning chemicals 

This is an easy and convenient solution. All it takes is to pour the liquid into the drain opening. You can also pour it down your sink or shower.

But don’t pour it down the toilet, as it won’t be effective at all.

A small amount of a safe chemical can clear the clogging without causing corrosion to the pipes.

FAQs On Can A Toilet And Shower Share The Same Drain

Do showers and toilets drain to the same place?

In most residential properties, the showers and toilet drain eventually connect to the same sewer.

Can you hook a shower drain to a toilet drain?

Yes, these can be connected with no issues so long as you ensure they have separate waste traps and the toilet drain has no opportunity of backing up into the shower drain. 

Are bathtub and toilet drains connected?

This depends on the plumbing in a specific building. Many will have their own drainage system but go to the same sewer. In more eco-friendly buildings, the two can be completely unconnected so the greywater can be recycled.

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