Everything You (Never) Wanted to Know About Airplane Toilets

Going to the bathroom on an airplane is about as exciting as a colonoscopy. But if you like to order a cocktail or two on a flight, this is one nook of the plane you can't escape.

While you're in there, though, a million questions probably leap into your mind: What's the deal with the disclaimer that says "Do not flush while seated"? Why are the flushes so loud? Why is the toilet water blue? Does frozen poop really fall from the sky?

Well, we asked those questions for you and got the answers. Here's everything you wanted to know (or maybe didn't want to know) about the plane's most underrated (and most active) room.

Modern Lav

When you fly, the pressurized cabin can make you want to poop. On an average long-haul 747 flight (let's say a 747-400 seating 416 in a typical three-class layout), the average passenger visits the loo 2.4 times during a flight, producing 230 gallons of waste — nearly the volume of a four-person Jacuzzi.

That's a lot of poop, and it requires a miracle of engineering to handle it all.

That's where the airplane-toilet flush comes in, a noise so loud it's as if the toilet bowl opened up to the skies to release its contents. No wonder rumors say the force of the flush is strong enough to suck the entrails right out of your butt!

The loud noise is certainly startling, and it's certainly nothing like when you flush the toilet in your house. Most in-house pots don't come with disclaimers, for one. More notably, there's no water in the bowl. Toilets on the ground, like the one in your bathroom, use siphons to flush — water enters the siphon and drains via gravity to a sewage system or septic tank.

But aircraft lavatories can't be built using siphons because water can't sit in a bowl on a plane because, well, spillage. Before the modern pots onboard today, spilling was a serious problem for passengers when slosh buckets and bottles were the norm — though there was no flush required, at least.

James Kemper invented a toilet to suit modern aviation needs, patenting the vacuum toilet in 1975. His invention was installed on Boeing planes by 1982, remedying the problems that the siphon toilet couldn't handle, like spillage. He added a nonstick bowl that used a blue substance known as Skykem to replace water and a powerful vacuum suction that left little to nothing behind. Skykem (the main ingredient in "blue ice") aids in killing odors and disinfecting the bowl. Plus, vacuum toilets use a lot less water than siphon toilets and are much lighter and can be installed in a number of ways, making them more efficient in terms of fuel and space, two things of paramount importance on planes.

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Where It All Goes

When you flush, a trapdoor in the base of the toilet opens and Skykem fills the bowl. The loud roar you hear when you flush isn't actually waste material exiting the plane into the atmosphere, despite the urban legends — it's the vacuum sucking the contents out of the waterless bowl. And it's not a small roar; the speed at which the contents exit the bowl have been clocked at a velocity faster than a Formula 1 race car.

From the lavatory, the waste travels through the plane's pipes to the rear of the plane and remains in a tank that can only be accessed from the exterior of the plane — pilots can't clear the tanks during the flight. The tank is emptied by special service trucks once the plane is safely on the ground. (Or, occasionally, not.) The trucks attach a hose to the aircraft, and it sucks out the waste into the truck. After the plane's tank is emptied, another hose is attached to both vehicles to clean the tank using a disinfecting product.

The 230 gallons of waste from an average long-haul 747 trip equates to 0.55 gallons per flush per passenger, which is significantly less than the 3.5 gallons land-based toilets go through per flush. But it's still nearly one ton in extra weight, or thousands of dollars in overweight baggage fees.

Load of Bull

While airplane lavatories once did come with disclaimers about flushing while seated, however ridiculous they seemed, there's no validity to the old horror story about the obese woman who had her inside sucked out on the airplane toilet, and it has never occurred to anyone. In fact, it's nearly impossible, since your butt would have to be completely airtight with the toilet bowl, which isn't possible with the toilet seat preventing a vacuum.

And as you now know, pilots can't eject the waste in the middle of a flight, even to lighten the aircraft's load. Not only is it illegal, it's just not a function built into the aircraft.

But, yes, there have been several cases over the past couple decades where homes have been hit by blue ice falling from the sky. The blue ice is a combination of human waste and Skykem that freezes at high altitudes and leaks out of a plane's undercarriage, dislodging closer to landing when the temperature rises. Who knew frozen poop could cause so much damage?

What's Next?

Vacuum toilets have been in use for over 30 years with minimal to no changes. But for the fussier among us, the loo's small space and sanitary nightmares are still reasons to sidestep the call of nature on a flight.

That could all change soon. In 2016, Boeing released a prototype of a new lavatory that's not only larger than typical airline commodes but also cleans itself. After each use, ultraviolet light shines on the lavatory for three seconds, killing 99.99% of pathogens left behind. The lights are positioned so that they hit all the important areas, like the toilet seat, faucet and countertops, and the toilet seat lifts and closes during sanitation so that all its surfaces are exposed to the UV light. The sanitizing even eliminates odor. The design also has hands-free faucets, soap dispensers, trash lids and a buttonless hand dryer. Boeing is also researching ways to incorporate a hands-free door latch and a vacuum-vent system to keep the lavatories as hygienic as possible.

Now with more knowledge than you ever needed about the porcelain throne in the sky, you can board your next flight and educate the folks too afraid to leave their seat when nature calls. Or you could just tell them to make like the 380,000 people who watched this video on how to use the bathroom on a plane.

Feature photo by Stuart Dee / Getty Images