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Should your toilet and shower share the same drain?
Room planning

Should your toilet and shower share the same drain?

Posted by Rebecca Doody in Room planning | 2 years ago 3 min read

The big question...

When rebuilding or planning your bathroom, it’s common to ask if the same drain can be used for both the toilets and showers. This question, however, has several different considerations that must be thought about before making a decision.

The general answer is that the showers and toilets can use the same drain, but they should not be sharing the same waste trap arm. There are other factors to consider as well, such as whether your drains lead to the main sewer line, or if there are septic tanks that are used in your city or town. All these different factors will affect if it is possible to combine the toilet drain and shower drain together, or if it is best to keep them as a separate drain line.

This article will go into detail on why these drains are normally exclusive from each other, and how different factors affect your overall choice on the feasibility of drain sharing.

Back to wall toilet

Greywater Vs Blackwater

The primary rationale behind having two separate drainage systems is due to two different kinds of water that must be kept apart in your plumbing network. This is because water from your toilet is way more likely to carry diseases compared to water from the shower.


Greywater is water that comes from the shower and is less likely to carry diseases, making greywater disposal regulations less strict. Greywater cannot be disposed of in any water body that is used as a drinking source. That would mean that disposing of greywater in rivers, streams and lakes are all no-gos.

At times, greywater disposal occurs in a separate septic tank, though this will depend on the type of home that you live in.

Though greywater can and is used to water plants and wash cars by some people, it is generally recommended to ensure that there are no harmful chemicals (soaps, detergents and shampoos especially) before using it on your plants.


Blackwater, however, is under strict regulation for its disposal due to containing high amounts of faeces and urine, making it a potent disease carrier and poses a significant risk to the health and safety of both humans as well as wildlife. This is why toilet drainage is important.

It is crucial to note that there are certain rules about disposing of water in a safe way. Sewage treatment facilities ensure that this is done properly. Blackwater is normally found kept in septic tanks, which will then be cleared at a sewage treatment centre when it is full. The toilet drain line is monitored.

Methods of disposal

There are a few ways that toilet waste and toilet water can be disposed of, depending on your situation and also the bathroom layout and bathroom floor plan.


If you’re in a motorhome or caravan, often sites offer services to remove both blackwater and greywater for disposal. This happens on campsites and certain dealerships also where the toilet lines will be different. Depending on where you are, petrol stations can also offer this service as well for your waste water, toilet drains and shower drains.

Low level shower trays

Fixed homes

For those living in fixed homes or a standard home with things like a tub drain, sink drain and drain pipe, your wastewater disposal, particularly blackwater, needs to be sent to a wastewater treatment centre for disposal, either through local plumbing or by bringing the septic tank to the wastewater treatment centre. Washing machine drains are also a factor to take into account when looking at your home as this is another plumbing fixture. Sink drains can be connected.

For more extreme cases, this may require a drive to larger cities that will have the water treatment capabilities available for use.

In both instances, you may find it useful to talk about this issue with others who live in the same area and see if they have contacts to any of the options you need. You may require services where plumbers connect drain lines. Just remember that it’s always important to dispose of wastewater properly.

How to deal with clogs

Another big issue lies with managing when sewer lines are clogged. The smell of the sewer in your own home or hearing weird sounds coming from your drains or drain pipe are prime indicators of a clogged drain.

These symptoms of clogs are often not from the drain in question, but often from a different drain that is connected, which most times is the shower and may be completely separate drain lines. This can lead to bad smells coming from your shower whenever you flush your toilet, for example. A flexible drain hose will reduce chances of clogs.


To fix this, chemicals may be needed to clear and tackle the main sewerage line pipe. This should be done with caution however, and is not always the best way to clear your drainage system. Ensure the chemicals you choose are safe, you are to go down this route. You must check if the chemicals are suitable for your piping system and main drain line, as the last thing we want is a smelly, leaking pipe and vent pipe due to overly-corrosive cleaning detergents.

Pouring these kinds of chemicals down the drain (within reason) may dissolve all the gunk and built-up debris in the waste pipes so that water can easily push it out of the way and into the drain system.

Drain snake

Alternatively, the messier but more-effective method of dealing with clogs is to use a drain snake, which either is rented or bought at most hardware stores in the area and assists with the plumbing vent. There are plenty of tutorials on both Youtube as well as other sites that go in-depth on its usage and how to use it most effectively.

To use a drain snake, you first will need to wear some rubber gloves, as you will be handling the contents of the clogged drain and main drain connection once it is pulled out. Next, you will remove the drain cover and then push the drain snake into the hole, feeding the tube down until you feel a blockage that doesn’t allow you to go any further.

You will rotate the drain snake while applying pressure onto the blockage and will keep doing so until you feel the blockage collapse. Once that is done, pull the drain snake back out from the hole. At its end, the drain snake will have the debris that was causing the blockage, so you must have a bin or bag that you will be used to dispose of the contents.

Should neither of these options work, it may be likely that the blockage is located further down the sewer line or in the main sewerage drain, or within the venting system, which would require the help of professional plumbers to assist you and get rid of that funky smell.

Shower heads and arms


In short, it is possible to connect the toilet drainage line and the shower drainage line, as long as they both have separate waste trap arms. However, do note that combining them may also lead to blockages, which can cause smells to come from certain drains.

Similarly, you also need to be wary of the difference between wastewater types and the corresponding methods of disposal to ensure that the health and safety of the surrounding area are not affected.

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Author, Rebecca Doody

Posted by Rebecca Doody in Room planning | 2 years ago

Originally from Somerset, Rebecca is our resident copywriter who takes care of all things product related. Rebecca loves the modern interior style with both neutral and bold influences to create a statement look.

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