This Is What Happens When You Flush Your Toilet

A typical sewer system is clearly explained in Concerning Reality's video.
Jessica Miley

Next time you need to go go to the toilet, think about gravity. Yes, that’s right that the underlying physics principle is how your waste gets from your ceramic bowl to your local waste treatment plant.

And while you are there give thanks to the modern sewer infrastructure. Before piped sewer systems put our waste out of sight and out of mind, cities had open sewers where was floated on open cut canals. Which was, well, exactly how you imagine.

Every time you use your sink, shower or toilet waste is flushed away into our wastewater system. It important to take special care with waste from our toilets as our fecal matter contains potentially deadly bacteria that can be harmful, not only that it stinks.

This video from Concerning Reality follows the journey of your waste from flush to arrival at the waste treatment facility. 

In ideal systems, the pipes containing wastewater uses gravity to push it wards the waste center. Pipes from each house or building are dumped into a more major pipe that normally follows alongside a road. 

These pipes are between 3 and 5 feet in diameter. This main sewage line has periodic vertical pipes with manhole covers to allow access to the pipe if needed. 

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These main lines may meet progressively larger and larger pipes as they continue towards the treatment center and gather more waste. Treatment plants are typically in low lying areas to assist with the use of gravity.

But of course, not every urban area can do this. Hills, rivers, and valleys mean that in some cases, sewerage pipes need to pressurized in order to get to the treatment facility.

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