It falls there, mostly
How Does Water Climb to the Tap?
Water is stored above your house, and that height alone provides the pressure at your tap.
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Step 1 of 5
The water starts higher than you do.
Every supply has a tank on a tower, a hill or a rooftop. Pumps fill it slowly, and that stored height is what feeds every tap below.
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Step 2 of 5
Height is the same thing as pressure.
The weight of all the water above a point presses down on it, so the further below the tank you are, the harder the water pushes.
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Step 3 of 5
Water will rise nearly back to its source.
Pressure will lift water almost to the level it fell from, which is why upstairs taps still run but noticeably more weakly than downstairs ones.
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Step 4 of 5
A tap is just a leak you control.
Turning the handle screws a rubber washer down onto a seat, pinching the flow. Open it and you are simply allowing the pressure to escape.
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Step 5 of 5
Tall buildings must add their own pumps.
No tower is higher than a skyscraper, so tall blocks pump water to a roof tank and let it fall back down to the flats beneath.
Every 10 metres of height gives roughly one bar of water pressure, about the same as the whole atmosphere pressing down on you.
The short version
Water reaches your tap because it is stored high above you, and that height alone supplies the pressure that pushes it through the pipes.
Try it yourself
Fill a bottle and make a small hole near the bottom and another near the top. The lower hole squirts much further, with more water above it.
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