Where Does Toilet Water And Poop Go After Flush?

The sewerage system has developed a lot since the Minoans built the latrines before 800 BC. But even now, despite all the rehabilitation systems and development projects happening, most people still have no idea where does toilet water go.

Well, toilet water goes down a complicated system of sewer pipes and ends up in a treatment plant where the harmful substances are removed. And these kinds of stuff are not a concern only for the plumbers.

To become a sensible citizen and/or a homeowner, having knowledge about these things are mandatory. In this article, I am going to explain where the toilet water goes and how toilets work.

How Does Flushing Work?

The plumbing system of a house or any residential building consists of many pipes. They take in all the wastewater from your daily usage, be they from toilets, kitchens or laundry rooms, or your showers, tubs, etc.

The wastewater contains soap, dirt, oil, food waste, human waste, urine, and toilet paper, and it is known as sewage. Then, the sewage is flushed down to pipes. But this is a process with multiple stages that I am going to explain in the next section.

The whole process of this water cycle is divided into two stages – the indoor stage that happens within your property and the outdoor stage that runs outside.

Indoor Stages:

First, let’s know the names of the different parts of your WC, AKA water closet.

Tank filling

The water closet is connected to a water supply. When the tank is empty, the fill valve is turned on and brings water from the water supply into the tank. Water will rise through the fill valve’s base, through the refill tube, and into the overflow tube that is connected with the flush valve.

As the water rises in the tank, the float ball rises too and shuts the valve. This entire thing happens within less than 60 seconds.


When you press that button on your tank, the flush lever is pushed, and all the water from the tank goes to the bowl, after which the flush valve closes. The decrease in water level makes the float ball drop.

Now the inlet valve is opened, and more water gets into the tank. The pressure of the new water keeps the valve closed. With the siphoning effect, through the U-shaped pipe, the water flushes down the waste to the toilet trap.

Dual flush WCs have two buttons for different quantities of water. The flushing process continues for 15 seconds at max.

Toilet Trapway

The toilet Trapway is the narrow, curved passageway that passes the waste along with the water to the toilet drain. But to control the bad sewer gas odors from spreading in the bathroom, the Trapway keeps some water as a shield.

Toilet Drain

All the flushed content from the toilet trapway goes into the toilet drain, a network of pipes collecting wastewater from other parts of your house, reaching the main sewer pipe. That is how all houses have their drains connected.

Sometimes people have their own septic system with a tank to collect the wastewater, where it is filtered and treated so it can be mixed into the soil. Also, these are generally away from municipal water systems.

You can also read the article: 3 Inch or 4 Inch: What Size Pipe is Best For Your Toilet Drain?

Outdoor Stages:

To use water resources efficiently, we recycle wastewater. The raw, unfiltered one is not to be released into the environment, for it will contaminate the soil and other water resources. So how do we treat this dirty water?

Wastewater treatment depends on two things-

Wastewater level or consistency

Drains carry wastewater from washrooms, kitchens, laundry rooms, roofs, etc. The water has a different level of consistency. WC flushes out the human fecal matter, menstrual blood, and urine and occasionally vomits.

Kitchen sink pipes pass oily, greasy, soapy water. During treatment, the same kind of wastewater is filtered together for reuse or ground release.

Purpose of reuse

Not all of the wastewater gets to be reused. Some are partially treated and released into the ground. However, some of it is treated and reused for the same toilets to avoid wasting natural resources.

If the purpose is bigger, like agriculture, fisheries, and irrigation, then there is a complex treatment system that I will explain to you in the next section. This treatment procedure is applicable only for the wastewater that the municipality water treatment plants collect.

The personal septic systems use a similar sedimentation process before disinfection and treatment of the effluent. After this, your wastewater is disposed into a drain field generally. Other times, it is disinfected and used for your lawn irrigation.

Stink Control

Before anything else, to protect the air pollution, strong chemicals are used in the plants to suppress the nasty choking stench that the sewage produces. Some systems use deodorizing misting agents too.


The sewage often contains larger solid materials like wipes, toilet paper, accidentally dropped diapers, tampons, menstrual cups, etc. These can be hard for machines and thus need to be removed. So the wastewater goes through a screening process to filter these solids out.

Initial Treatment

Then the water is transferred to ginormous circular settlement tanks where it is kept for an amount of time so that the next round of muck, mainly human waste, is accumulated at the bottom of the tanks. This settled pile is called ‘sludge.’

There are scrappers in the circular tanks to help the sludge pile up and move towards a different treatment machine. The water is now free of sludge and is prepared to go to the secondary treatment phase.


The water goes into a rectangular tank where it is whirled in order for the gas to be released. There might still be some organic elements left in the water after the previous phase. So, the air is now pumped into the water to create a bacteria-friendly environment. Then bacteria can decompose that organic leftover.

 Secondary Filtration

Natural soil itself provides decent filtration and treats the dirty water before it seeps into the soil. But even natural soil has its limits. Partially treated sewage goes through a sand bed screening, and that is how iron, bacteria, odor, solid materials, etc., are removed.

Vaporizing Solids

The solid and semi-solid stuff scraped will go for further treatment, where they will be heated until they break into methane gas and bio-solids that are full of nutrients.


In this stage, the bacteria are killed with chlorine, and the water becomes clean enough for reuse. This final phase is mandatory for effluents that later on go for irrigation or agricultural land uses.

So your toilet water has gone through all the treatment stages and is now ready to be finally released into the natural water bodies without any risk of water contamination.

Does Toilet Water Go into the Ocean?

Most of the toilet water from homes near coasts ends up in rivers or oceans. However, they are treated before to have all germs and pollutants and further tested to ensure they do not cause any environmental pollution.

Polluted water can not only harm aquatic plants and animals but also disrupt the ecological balance. It can also make people sick.

Where Does Toilet Water from Planes Go?

If you ever wondered if toilet water from planes drizzles down and on top of unsuspecting people’s heads and lands, then you’re not the only one. Well, the ‘whoosh’ is indeed the sound of all the waste being sucked out, but it is then reserved in a holding tank.

This tank remains at the back of the plane, away from the passengers, and is sealed tight. So, you don’t ever have to worry about it leaking and flooding the plane. Once the plane lands, the tank is emptied into the underground sewerage system.

Concluding Thoughts

From here, you should have a general idea about where does the toilet water go, and you can be careful about using your WC. Because if we don’t save water, it will be our future generation that will suffer.

Hello, I'm Jon C. Brown, an expert in the field of toilets. With over 15 years of experience in this industry, a significant portion of my life has been devoted to crafting high-quality toilets and bathrooms. Consequently, I've received countless inquiries about the toilet and bathroom industries. That's why, I've launched this website to provide top-notch solutions for all your toilet and bathroom related needs.

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