What Actually Happens When You Flush an Airplane Toilet?

Everything you've always wanted to know about airplane toilets but were too polite to ask.

what-happens-when-you-flush-an-airplane-toiletiStock/guvendemir, iStock/tzahiV

If you’ve ever imagined pee or poop dropping out of an airplane like a surprise crop-dusting, that actually used to happen. Early airplane toilets were primitive and direct: a bucket or bottle. The contents were simply hurled out of the window onto the unsuspecting world below. However, once commercial flying become popular and pressurized cabins were introduced, they had to develop a new system.

That’s when airlines introduced a toilet using Anotec (a blue deodorizing gel) to flush away waste and combat odor. But this meant carrying gallons of Anotec, which was very heavy, causing planes to waste precious fuel and limiting passenger space. Storage tanks were also directly underneath the toilets, so the smell sometimes drifted up into the cabin—not something you want when you’re tucking in to your in-flight meal!

Toilet waste also had an unpleasant habit of leaking onto the outside of the aircraft, where it froze. As the plane descended, lumps of icy gel and feces sometimes plummeted to earth at great speed, reportedly damaging cars and houses below.

In 1975, James Kemper designed the modern airplane toilet, using a non-stick bowl, a small amount of Skychem (disinfecting liquid), and powerful vacuum suction. When you flush the toilet, a trapdoor in the base opens, liquid is released, and everything is sucked out faster than a Formula 1 racing car. Waste whizzes through pipes to the rear of the plane, where it’s stored in sealed tanks well away from passengers, until the plane touches down. Travelers on a long-haul 747 flight will flush the toilets around 1,000 times and create around 230 gallons of sewage—that’s a lot of waste! When the aircraft lands, a ‘honey truck‘ siphons out the waste and disposes of it into the ground sewage system.

In case you’re wondering whether pilots can accidentally empty the tanks in flight, delivering a nasty shock to anyone underneath, the door has external clips to prevent such unexpected accidents. And if you’ve heard the urban myth about toilet vacuums sucking out your insides, don’t worry. It’s like other common airplane myths—there are no recorded incidents.

Flying puts strain on your body, so don’t make it worse by holding in poop, which can cause serious digestive problems. Now that you know how airplane toilets work, there’s no need to sit tight on a flight ever again.

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