What goes on in the bathroom stays in the bathroom — but what does go on in an airplane bathroom? Toilets are a kind of taboo topic for many people, as the bathroom is the one room in any building we can count on for any alone time. But that doesn’t mean we don’t have questions about where all the waste goes when we flush our toilets!
Before we can get into how an airplane bathroom works, we have to do a deep dive into how a traditional toilet works.
Airplane Toilet 101
The average toilet you’ll see in a residential home is typically a porcelain bowl connected to a tank that fills said bowl with water after every flush. The waste is flushed from the bowl, out through the connected plumbing, and into either a sewer system or a connected septic tank, depending on where you live.
The method of waste removal is great for a non-moving bathroom, but on trains or airplanes (methods of travel that usually have restrooms onboard), turbulence and motion don’t mix well with an open bowl of toilet water. Enter: the vacuum toilet.
Vacuum toilets are the stereotypical toilets you’ll see on transport services. These toilets don’t use a siphon and gravity to flush waste in the same way a traditional residential toilet does. Instead, vacuum toilets feature a valve inside the sewer line to suck all the content of the bowl out. The waste is collected in a separate tank that needs to be emptied out on arrival.
The suction of the valve creates the loud noise you may be familiar with if you’ve ever been on a plane. The benefits of this system as convenience and hygiene — the vacuum method means that toilets have to use less water and/or sanitizing liquid in the flushing process to keep the bowl and line clear.
Other than hygiene, this system also uses significantly less water than the traditional home toilet does. Vacuum systems can flush with half a gallon of water, whereas a low-flow siphon toilet uses about 1.6 gallons. In contrast, older, non-efficient models can use up to 5 gallons per flush!