What Actually Happens When You Flush an Airplane Toilet?

During a given flight travelers flush the toilets up to 1,000 times—here's what happens to all that sewage.

what-happens-when-you-flush-an-airplane-toiletiStock/guvendemir, iStock/tzahiV
If you’ve ever imagined the contents of your airplane toilet dropping out the bottom of the plane like a surprise crop-dusting, that’s just one of 50 airplane facts everyone’s always curious about. And it’s not so far-fetched; this actually used to happen. The very earliest airplane toilets were primitive and direct: think bucket or bottle. Passengers simply hurled the contents out the window onto the unsuspecting world below. It may seem kind of déclassé, given how glamorous early flying looks in vintage photos, that the toilet systems would be so subpar. But once commercial flying became popular and pressurized cabins were introduced, bathroom systems saw an upgrade as well.
Airlines introduced a toilet that used Anotec—blue deodorizing gel that flushed away waste and combatted odor. It wasn’t without its problems; airlines had to store gallons of the stuff, which was very heavy and resulted in planes wasting precious fuel and having to limit passenger space. In addition, the storage tanks were directly below the toilets, so the smell sometimes would drift up into the cabin—not something you’d want to experience before tucking into your in-flight meal!
These early toilets weren’t fool-proof. Toilet waste sometimes leaked to the outside of the aircraft, where it froze. As the plane descended, it would drop icy lumps of blue gel mixed with feces, which sometimes plummeted to earth at great speed reportedly damaging cars and houses below.

In 1975, James Kemper designed the modern airplane toilet that featured a non-stick bowl, a small amount of Skychem (disinfecting liquid), and powerful vacuum suction. Now when you flush an airplane toilet, a trapdoor in the base opens, liquid is released, and everything is sucked out faster than a Formula 1 race car. Waste whizzes through the plumbing to the rear of the plane, where it’s stored in sealed tanks, well away from passengers, until the plane touches down. On a long-haul 747 flight, travelers might flush the toilets around 1,000 times, creating 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 airport’s underground sewage system.
In case you’re wondering whether planes might accidentally empty the tanks in flight, delivering a nasty shock to anyone below, not to worry; the door has external clips to prevent such unexpected accidents from occurring. And if you’ve heard the urban myth about toilet vacuums sucking out your insides, that’s not likely either; at least, there are no recorded incidents to date. In short, using the facilities is definitely not one of the 18 things you should never do on an airplane.

Elizabeth Manneh
Elizabeth is an experienced freelance writer, specializing in health & wellness, education & learning, family life & parenting, and women's issues. She's been published on Huffington Post, and was a regular contributor to Love Live Health and Daily Home Remedy. Elizabeth is a retired primary school principal and education consultant, with a continuing passion for education and learning. She's familiar with writing newsletters, reports to stakeholders, financial reports, business plans and evaluation reports.