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Dominating the skylines of urban metropolis around the world are the gravity-defining skyscrapers soaring higher than any building has dared to climb.
We're not here to talk about the iconic architectural wonders of the spectacular modern world. No, instead, we're talking about the mechanical issue of how your crap is disposed of hundreds of metres up from the ground without making a shitty mess when it lands.
Turns out it's rather a tall order, and one that we haven't thought about before, which could be down to the best-designed toilet systems operating without our awareness of its existence.
"The basic thing to remember is the poo hits terminal velocity - just like a sky diver," drainage expert Mark Briggs told Mirror Online. "It does bounce back up at the bottom, though, so the drainage needs to be designed to stop that."
It's all down to the angle at the bottom of the pipe, believes Briggs. The trick is much similar to a water flume. To slow down, the pipe levels out, to speed up, they become more vertical (simple lesson in gravity there).
In order to prevent blockage - while also controlling the flow of waste - the pipe has to adhere to building regulations standards on the angle of pipes.
This allows the flow of waste to follow a turn in the pipe to then flow horizontally and into a drain, where flow increases, which is dependent on the entrance velocity, depth of water and pipe diameter among other things.
For buildings exceeding five storeys, the bottom two toilets have to be on their entirely own stack in order to avoid any mess. It is in fact a 'bounceback', where waste will begin to discharge, at speed, out of the ground floor amenities. Think Jackass flying toilet - nobody wants to clear that up.
So, the first thing engineers need to consider when designing a skyscraper's toilet is the number of appliances needed in the building, each of which is given a discharge unit.
This is a measure of how much fluid is expected to produce in any given appliance - that's everything from a toilet, shower, sink etc, because a sink will produce less waste than your hotel toilet.
A complicated formula collected using these two numbers will then result in the litres per second of liquid that you can expect to get rid of down the toilet system, which will then tell the specialist the size of pipe that will be required to do the job effectively and efficiently.
Other factors that are considered are what the pipes are made out of. PVC is the material of choice in domestic properties, but larger buildings will commonly use cast iron to protect them from rats, fire and the vast amount of waste which travels through under high pressure.
The other thing to realise is that if high-rise buildings were to rely on a single plumbing system, then the people at the top of the building would have no pressure. Instead, they employ a number of plumbing systems, each serving an area of the building. So, if you were thinking of flushing all the toilets in the 830-metre-high Burj Khalifa, then you wouldn't destroy the building. Engineers win.
Words: Hamish Kilburn
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