How do aeroplane toilets work?
Aeroplane loos don’t work like your toilet at home, which uses water and gravity to move waste into the sewer system. Instead they use a strong vacuum, along with a blue chemical that cleans and removes smells every time you flush.
A stinky tank
This sucking system is very much like the vacuum cleaners people use at home to remove dirt and dust from their floors. This dirt and dust ends up in a container that you empty into a rubbish bin. Similarly, the waste and the blue cleaning fluid from the aeroplane’s lavatories ends up in an underfloor storage tank, at the very back of the plane’s cargo hold. With so many people on a plane needing to use the toilet, you can imagine how big this tank has to be.
The vacuum pressure system moves all the solid and liquid waste from the toilet along a plumbing pipe that connects to the storage tank. There is a valve on the storage tank that opens when the loo is flushed and snaps shut when the toilet is not in use. This prevents foul odours escaping from the tank. This, along with the blue chemicals, helps keep the stink down.
What happens when the plane lands?
Once the plane has touched down on the ground, a special truck comes to meet it. A large hose is plugged into the waste tank valve and sucks out all the poo and wee into a container on the back of the truck.
Once everything has been emptied from the aircraft, the truck is driven to a special area at the airport where the waste from all the aeroplanes goes. From here, all of this faecal matter (a posh way of saying “poo”) is emptied into the airport’s sewer system. Driving this truck is a very important – and delicate – job. It takes three days of training for operators to learn how to use it.
FAST-FLYING FAECES On some planes waste zips into the storage tank at speeds of up to 130 miles per hour.
Watch out for blue ice
It has been reported that sometimes the valve that allows the truck to connect to the aeroplane’s waste tank can leak a small amount of the waste and blue chemical. This happens more often on older planes. The outside temperature at a normal cruising altitude of 10,000 metres is around -56°C, so the chemical turns into what is known as “blue ice”.
This blue ice remains attached to the plane as long as the temperature remains below freezing. However, as the aeroplane descends the blue ice begins to thaw, and may even fall off. There have been several occasions reported in the news where people have witnessed this flying poo.
FLUSHED WITH SUCCESS On a long-haul flight, the onboard toilets may be flushed more than 1,000 times.
In-flight dumping
In case you were wondering, the captain of the plane doesn’t have a button to release all the poo and wee from the storage tank while the plane is flying. Any waste that might leak out of the plane would be totally accidental.
Some people do think that aeroplane contrails (the white lines aircraft sometimes leave behind them in the sky) are either a special mind-control chemical or the toilet waste. Neither is true. What you are actually seeing is water vapour from the engines turning into solid crystals of ice, and forming a thin cloud in the sky.
