WEBVTT - How does an airplane toilet work?

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<v Speaker 1>Welcome to Brainstuff from how stuff works dot com where

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

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<v Speaker 1>the toilet and a commercial airliner work? If you've read

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<v Speaker 1>the house stuff Works article entitled how toilets Work, then

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<v Speaker 1>you know my philosophy on this kind of stuff. Toilets

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<v Speaker 1>have a very bad image because of what we put

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<v Speaker 1>into them, but if you can get past that and

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<v Speaker 1>focus on the technology behind them, toilets can be pretty

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<v Speaker 1>amazing devices. The typical home toilet uses a bowl filled

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<v Speaker 1>with water. When you flush the toilet, it starts a

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<v Speaker 1>siphon that drains the bowl. Gravity then carries the water

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<v Speaker 1>into the septic tank or the sewer system. The problem

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<v Speaker 1>with this approach on an airplane or a train, or

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<v Speaker 1>a bus or a boat or whatever is that the

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<v Speaker 1>motion of the vehicle means you can't use a bowl

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<v Speaker 1>of water. It would splash out every time there was

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<v Speaker 1>a little turbulence. Since there is no bowl of water,

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

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<v Speaker 1>So airplane toilets use an active vacuum instead of a

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

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<v Speaker 1>it opens a valve in the sewer line, and the

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<v Speaker 1>vacuum in the line sucks the contents out of the

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<v Speaker 1>bowl and into a tank. Because the vacuum does all

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<v Speaker 1>the work, it takes very little water or that blue

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<v Speaker 1>sanitizing fluid used in airplanes to clean the bowl for

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<v Speaker 1>the next person. Most vacuum systems flush with just half

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<v Speaker 1>a gallon or two liters of fluid or less, compared

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<v Speaker 1>to the one point six gallons or six liters of

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<v Speaker 1>water for water saving toilets and up to five gallons

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<v Speaker 1>for an older toilet. It turns out that vacuum toilets

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<v Speaker 1>have lots of other advantages even in normal installations. They

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<v Speaker 1>do use very little water, They can use much smaller

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<v Speaker 1>diameter sewer pipes. They can flush in any direct action,

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<v Speaker 1>including upward. Sense a vacuum system doesn't use gravity to

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<v Speaker 1>move the water, there's nothing to stop the sewer pipe

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<v Speaker 1>from going straight up, and they can be put anywhere

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<v Speaker 1>in the building. For more on this and thousands of

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<v Speaker 1>other topics, because it how stuff works, dot com