How Do Airplane Toilets Work?

Q: I was recently on a transcontinental flight from New York to Los Angeles and had a bathroom emergency midway through the flight. (Now that I think about it, it might have been that triple-cheese burrito I scarfed right beforehand.) On my third trip to the loo (which was fortuitously unoccupied at the time), I wondered — how do airplane toilets work? I mean, there doesn’t seem to be much water in them or much place for the waste to go. And now that we’re on the subject, where does everything in the plane's toilets go? It doesn’t just get dumped in the sky, does it?

A: “Cloudy with a Chance of Poo” coming to theaters this spring. Can you imagine walking down the street, minding your own business, when suddenly, you get dumped on by someone else’s business? Ich. To answer your question — no, airlines don’t just dump waste from the plane’s toilets as they fly through the air, but we’ll get to that later. Let’s first discuss how airplane toilets work in the first place.

Most regular toilets (like the ones found in your home) are also known as gravity toilets because (shocker alert) they rely on gravity to work. The water that rushes down into the toilet bowl when you flush forces the water to go down and out the pipes. You can actually simulate a toilet flush by quickly pouring in a large amount of water into the toilet bowl. (I know this from my year abroad in college — where, at the most inopportune times, the toilet would simply stop working.)

On a plane though, the same system doesn't work very well — just think about all the water that would be sloshing around the bathroom every time the plane hit turbulence. Instead, airplane toilets use a vacuum system to work. You know that very loud, unnerving sound you hear each time you flush the toilet in an airplane bathroom? The one that makes you think an engine just exploded? That is actually a vacuum suctioning waste away. The blue liquid that is left in the bowl afterward is usually just a small bit of sanitizing solution to keep the bowl clean.

So what happens after your deposit is suctioned out of the toilet? It goes into a tank that is properly emptied and disposed of by a sanitization crew at the airport. And contrary to urban legend, pilots do not dump the waste midflight. In fact, they couldn't dump the waste in mid-flight if they wanted to — because the lever to open the tank is located on the outside of the plane and can be opened only by a lavatory waste crew once the plane is on the ground (or a very skilled goose).

So you’re worried about something hitting you from that big toilet in the sky? The Federal Aviation Administration (FAA) says it’s near impossible for that surprise from the sky to be human waste, and it’s more likely that it’s from a passing bird. I know what all you conspiracy theorists are saying: “Of course the FAA would say that,” right? Well, for those of you who aren’t so sure, check out this woman’s story and decide for yourself. Now that I think about it, “Cloudy with a Chance of Poo” might make an entertaining flick after all.

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