General Question

2davidc8's avatar

How is water pressure generated?

Asked by 2davidc8 (7741points) July 17th, 2014

The water from our taps, faucets and hoses comes out with considerable pressure. I’m wondering how is this pressure generated, especially since it has to be distributed to so many houses, each with many faucets, taps, toilets, showers, etc. And the water has to go the top floor of high buildings.

I’ve seen water tanks on hills, so is the water generated by gravity? Even so, I can’t imagine how this alone is sufficient to generate enough water pressure for everybody.

Can someone explain?

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8 Answers

XOIIO's avatar

It depends where you are, but it all comes down to water pumps, same as you pressurize air or gas to fill your car.

I don’t get how you never figured that out.

2davidc8's avatar

@XOIIO So, are the water pumps that powerful?

cazzie's avatar

It depends where you live, but yes, the towers are enough in most flat lands. There are also usually pumping stations at critical points that treat the water. My small town where I grew up has a tower and a pumping station where the water quality is monitored. (My brother in law in in charge of it, so I was lucky to get some insight into it. He uses a spectrometer to make sure radon limits aren’t exceeded.) If you want to learn more about it, perhaps you could organise a visit to your local water works facility.

Water pressure is usually regulated as water comes into the home by a regulator. It looks like this:
Because the water runs through a system of ever decreasing pipes, this actually accumulates a great deal of pressure on its own and the PSI has to be brought down by a regulator to save on strain in the pipes.

In some homes, especially those on hills (like where I lived in New Zealand) our hot water tanks and other holding tanks would be installed in our roofs to assist in increasing water pressure. This is also why tall buildings have water tanks on their roof because municipal water psi would become useless in the top stories, so they have to have their own system to build pressure in their internal pipes.

I hope this helps explain some of your question. Liquid dynamics is really more exciting than people think and we take it all for granted when we turn on our tap.

Here is a good ‘How Stuff Works’

XOIIO's avatar

@2davidc8 They make hydraulic pumps that can exceed 5000 PSI no problem, large capacity water pumps are no problem. The main water facility sends the water out quite a long ways, if it needs to go further, it goes through a substation. For apartment buildings like in new York, they use water tanks to help. The water pressure from the main lines can only go up so far so the apartment building will have a fairly powerful pump that send water up to fill the tank, and then gravity is what supplies the water to the building. It’s much easier since the pump they have could not supply a lot of usage at once, and one that could would be too noisy.

SecondHandStoke's avatar

Water pressure in New York apartments.

I can assure you from experience that there is no such thing.

Seriously. You can tell a residential building has greater than five stories at a glance in New York. It will have a tank on top.

Buildings five stories or lower are pressurized by gravity’s effect on the water from the Catskills.

CWOTUS's avatar

Calculating water head pressure is no great trick, since it’s just based on height of the column of water.

Where engineering and planning come into play, though, is estimating the amount of supply / flow that may be required at times of maximum demand. That’s why some water mains are larger than others, because small neighborhoods don’t require huge water mains to supply relatively low volumes of water, but a city containing numerous high-rise apartment buildings, commercial and industrial users, will need to have a much higher capacity to deliver sufficient flow.

But pressure is simply a function of height (in gravity-fed systems), or the capacity of the pump for mechanically-pumped service.

2davidc8's avatar

Wow! I didn’t realize they made water pumps that powerful.
Thank you for enlightening me.

boffin's avatar

How is water pressure generated?
That’s what all those water towers are for. Municipalities pump the water up, gravity does the rest.

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