Speaker 1: Welcome to Brainstuff from how stuff works dot com where
Speaker 1: smart Happens. Hi'm Marshall Brain with today's question, how does
Speaker 1: the toilet and a commercial airliner work? If you've read
Speaker 1: the house stuff Works article entitled how toilets Work, then
Speaker 1: you know my philosophy on this kind of stuff. Toilets
Speaker 1: have a very bad image because of what we put
Speaker 1: into them, but if you can get past that and
Speaker 1: focus on the technology behind them, toilets can be pretty
Speaker 1: amazing devices. The typical home toilet uses a bowl filled
Speaker 1: with water. When you flush the toilet, it starts a
Speaker 1: siphon that drains the bowl. Gravity then carries the water
Speaker 1: into the septic tank or the sewer system. The problem
Speaker 1: with this approach on an airplane or a train, or
Speaker 1: a bus or a boat or whatever is that the
Speaker 1: motion of the vehicle means you can't use a bowl
Speaker 1: of water. It would splash out every time there was
Speaker 1: a little turbulence. Since there is no bowl of water,
Speaker 1: you can't use a siphon or gravity to empty the bowl.
Speaker 1: So airplane toilets use an active vacuum instead of a
Speaker 1: passive siphon. They're actually called vacuum toilets. When you flush,
Speaker 1: it opens a valve in the sewer line, and the
Speaker 1: vacuum in the line sucks the contents out of the
Speaker 1: bowl and into a tank. Because the vacuum does all
Speaker 1: the work, it takes very little water or that blue
Speaker 1: sanitizing fluid used in airplanes to clean the bowl for
Speaker 1: the next person. Most vacuum systems flush with just half
Speaker 1: a gallon or two liters of fluid or less, compared
Speaker 1: to the one point six gallons or six liters of
Speaker 1: water for water saving toilets and up to five gallons
Speaker 1: for an older toilet. It turns out that vacuum toilets
Speaker 1: have lots of other advantages even in normal installations. They
Speaker 1: do use very little water, They can use much smaller
Speaker 1: diameter sewer pipes. They can flush in any direct action,
Speaker 1: including upward. Sense a vacuum system doesn't use gravity to
Speaker 1: move the water, there's nothing to stop the sewer pipe
Speaker 1: from going straight up, and they can be put anywhere
Speaker 1: in the building. For more on this and thousands of
Speaker 1: other topics, because it how stuff works, dot com