Why do taps have that one extra trickle of water a few seconds after they’ve been closed?
In: Engineering
That’s (some of) the water that’s in the part of the tap that is between the valves that open to allow water to flow and the end of the spout.
A very very crude ASCII representation of the flow of a pipe and spigot might look like this
water source ———X——– tap
Where the X is the valve that cuts off the tap from the water source.
Now this just shows essentially a flat view, but typically there is some part of the spout that is past the valve and also goes down (or else it would just spurt out the end across the kitchen/bathroom); the bit of water that is still going out maintains momentum and if it’s in front of the X with regards to the tap, it’ll keep coming out.
EDIT: Another way to look at it is like this: Say you have a million people all pushing on a door, that can only fit through maybe 2-3 people at a time, and in the door immediately there’s a fairly small hallway beyond which there’s a big department store. If you open the door to let people in on Black Friday and they storm in the hallway, once you close the door again, anyone who has made it to the hallway will still trickle out into the Wal-Mart.
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