How does an airplane toilet work at 10,000m?

"With almost anything on an airplane, you realize how much work it takes from an engineering perspective, even just a meal. Everything on an airplane is twice as hard as it is on the ground," Al St. Germain, an aviation industry consultant who has worked for airlines including Delta and United, told CNN.

No water used

Using water to flush the toilet on an airplane is not recommended due to the weight restrictions of the plane. There is no problem because the plane uses air instead.

The standard evac system uses differential air pressure to clean the tank, following a design originally patented by James Kemper in 1975.

Waste bins - where everything goes down the toilet - are usually located at the back of the plane and sometimes at the front.

Airplane lavatories have remained largely unchanged since 1975, when James Kemper patented the vacuum flushing system.

When you press the flush button, a valve opens at the bottom of the toilet, connecting it to the pipe below. This pipe—and the waste tank—is under pressure, which means opening the valve creates a vacuum that sucks up what's in the tank.

“It’s like a vacuum cleaner,” said Nigel Jones, an aircraft engineering expert from Kingston University in London who is also a member of the UK’s Royal Aeronautical Society. “When you press the button, the valve opens, and as soon as the valve opens, the suction sucks everything out. Then the valve closes.”

That vacuum effect happens all the time when the plane is in the air, Jones says, and you just don't hear it until you open the valve and connect the tank to the system. But when the plane is on the ground, there's no pressure differential—which means the tank is drained by a pump, which creates a vacuum in the tank. As the plane rises into the air and the pressure difference inside increases, a vacuum naturally forms and the pump stops. The pressure differential clears everything out quickly."

Airlines choose how many bathrooms they want on their planes. Jones says there is a minimum number for each plane, depending on size, but airlines can exceed that number if they want.

Is it released into the atmosphere?

Of course, a full container needs to be emptied and that's where the "wagons" come in. These are airport service vehicles that empty the container and transport it for disposal within the airport grounds.

It’s a process that’s been engineered for 50 years. Jamco, a Japanese company that now has 50% of the aircraft lavatory market, has pushed the boundaries of engineering to build in-flight lavatories. They were also the first to introduce hygienic touchless faucets and flushes on the Boeing 787.

Jones said planes have never intentionally dumped toilet waste into the atmosphere, even in the old days. But if a leak occurs in the exhaust pipe, because the temperature of the air is well below freezing, any liquid that comes out will automatically freeze, which is known in the industry as “blue ice.”

New generation aircraft such as the Airbus A350 have revolutionized the circulation of air on aircraft.

Since the 1980s, a rule has been in place prohibiting takeoffs when an aircraft's toilet system is leaking.

However, the accident still happened in 2021, people near Heathrow Airport in London were "dumped" with feces. Worse, it didn't even freeze because the plane was close to the ground and not in freezing temperatures. Luckily, that's a rare occurrence.

However, toilet blockages on airplanes happen frequently due to many reasons, including passengers leaving items out of curiosity to see if they will fall down.

It may seem like a harmless test, but it can cause flight delays and expensive repairs because there are a lot of pipes that have to be broken down to find the blockage. If one or two toilets are blocked, the plane will have to land because a certain number of toilets are needed for passengers.

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