Frequent flyers pay a visit to their aerial waste disposal system fairly often, and certainly they have caught themselves asking a simple question. How does this toilet work? It appears to have a minuscule amount of water or the blue sanitizing goop often associated with public toilets and outhouses. So how does the toilet flush? And where does the waste go? Don’t get too flush-strated trying to think about it! Let’s take a look at how airplane toilets function.
Airplane toilets function somewhat differently than regular toilets due to the extreme circumstances of being so high in the air. If the bowl was filled with water like a home toilet, the violent movements of the plane would cause the water to spill out of the bowl and splash around. Hardly sanitary or a desired outcome! To counteract this, airplane toilets use a vacuum rather than gravity to push the contents of the bowl out with little to no other liquid present at time of use. There will be a little bit of water or blue liquid used to cleanse the bowl during this step, but compared to commercial ground toilets it uses much less (2 liters for a vacuum toilet and 6 to 10 liters for a gravity toilet respectively). Thanks to the slickness of the bowl’s anti-stick surface, the waste is completely evacuated into the plane’s waste tank with no residue left behind!
By contrast, toilets found on the ground use a different system which is less water efficient. Upon flushing, a siphon system begins, draining the waste and water into a pipeline that uses gravity to pull everything out to the sewer or septic tank. It requires more water and energy, but since waste tank sizes aren’t a huge concern for homes and businesses this has remained a satisfactory design. More septic tank cleaning info here.On the plane, the size of a waste tank must be taken into consideration, as a heavier tank requires more fuel to carry, also sacrificing potential passenger weight limits in the process. This put pressure on engineers to come up with a better solution for airplanes as previous systems used more liquid per flush or simply ejected all waste from a vent on the body of the airplane. Modern airplane toilets are quite a technical marvel!
It may not be something you think about all the time, going to the bathroom is a frequent occurrence for us and toilets are something we take for granted. But a lot of thought has gone into the design of airplane toilets which need to provide us with this much needed service, especially on several hour long flights, so next time you’re on the latrine several miles up be sure to appreciate it!