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Speaker 1: Welcome to Brainstuff from how stuff works dot com where

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Speaker 1: smart Happens. Hi'm Marshall Brain with today's question, how does

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Speaker 1: the toilet and a commercial airliner work? If you've read

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Speaker 1: the house stuff Works article entitled how toilets Work, then

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Speaker 1: you know my philosophy on this kind of stuff. Toilets

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Speaker 1: have a very bad image because of what we put

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Speaker 1: into them, but if you can get past that and

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Speaker 1: focus on the technology behind them, toilets can be pretty

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Speaker 1: amazing devices. The typical home toilet uses a bowl filled

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Speaker 1: with water. When you flush the toilet, it starts a

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Speaker 1: siphon that drains the bowl. Gravity then carries the water

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Speaker 1: into the septic tank or the sewer system. The problem

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Speaker 1: with this approach on an airplane or a train, or

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Speaker 1: a bus or a boat or whatever is that the

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Speaker 1: motion of the vehicle means you can't use a bowl

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Speaker 1: of water. It would splash out every time there was

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Speaker 1: a little turbulence. Since there is no bowl of water,

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Speaker 1: you can't use a siphon or gravity to empty the bowl.

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Speaker 1: So airplane toilets use an active vacuum instead of a

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Speaker 1: passive siphon. They're actually called vacuum toilets. When you flush,

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Speaker 1: it opens a valve in the sewer line, and the

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Speaker 1: vacuum in the line sucks the contents out of the

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Speaker 1: bowl and into a tank. Because the vacuum does all

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Speaker 1: the work, it takes very little water or that blue

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Speaker 1: sanitizing fluid used in airplanes to clean the bowl for

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Speaker 1: the next person. Most vacuum systems flush with just half

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Speaker 1: a gallon or two liters of fluid or less, compared

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Speaker 1: to the one point six gallons or six liters of

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Speaker 1: water for water saving toilets and up to five gallons

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Speaker 1: for an older toilet. It turns out that vacuum toilets

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Speaker 1: have lots of other advantages even in normal installations. They

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Speaker 1: do use very little water, They can use much smaller

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Speaker 1: diameter sewer pipes. They can flush in any direct action,

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Speaker 1: including upward. Sense a vacuum system doesn't use gravity to

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Speaker 1: move the water, there's nothing to stop the sewer pipe

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Speaker 1: from going straight up, and they can be put anywhere

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Speaker 1: in the building. For more on this and thousands of

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Speaker 1: other topics, because it how stuff works, dot com