It seems like such a huge amount of water and would require so much energy to get it that high, plus there’s the waste to deal with
Waste is easy, it goes down.
For pressure, high rises have a pump in their machine room that pumps water upwards. It used to be water towers on the roofs of buildings that aides pressure
A bit of an elaboration on why water towers are used in combination with pumps. Pumps are great for moving a constant amount of water around at whatever rate the pump is designed for (e.g. a small pump will move something like 1 gallon per minute). a big enough pump (or series of smaller pumps) can cause that pumped water to consistently flow at that rate.
The problem is that people don’t use water at a constant rate. In the morning, several residents probably all run the shower at the same time. if too many people open the water tap at the same time, a pump will give each just a fraction of what they expect.
But a water tank high up supplies water by gravity, you could open a large number of water taps, and as long as the pipes from the tank are big enough they’d all have the same pressure as if just one opened.
The water is gradually pumped up to the tank no matter if people are using it or not, then when many people want water, they all get it at expected pressures and the tank start to empty. Eventually people close the taps, the tank will slowly start to fill again from the pump.
This same basic design is also how water towers supply water to many single story buildings, it’s not a unique engineering feat for skyscrapers, but an adjustment to fit somewhere within the building’s footprint.
And water towers are still used to manage water pressure demands in municipalities.
Yeah - if you’re in NYC at any point and go up anywhere you can see roofs of a lot of buildings, you’ll see a TON of water tanks and towers on older stuff.
Example:
(It’s not just older stuff, by the way. They’re actually still made of wood like that to this day, because it’s apparently the best way to do it.)
Yep, there’s a Dirty Jobs episode about it.
Oh neat! TIL!
Plumber here. Unless we’re talking about sky scrapers the grid pressure is generally enough to lift the water to the top floors. As long as it’s lower than the city water tower there’s no issue. If it’s a flat terrain or the building is on a hill then yes, you might need a pump to boost the pressure. Sewage on the other hand is not an issue - gravity takes care of that.
Can you recover energy on the way back down?
Classic sewage turbine.
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I’m no expert, but I’ve looked at this in the past. Most large buildings have their own water tanks inside them. If you think of an image of a New York skyline away from the skyscrapers you might picture small water towers on top of most of the buildings. Those are the tanks that supply water for the building. Skyscrapers will have multiple tanks inside the building itself, maybe one every 5 or 10 floors up. There will always be one at the top of the building but it might not be as obvious looking as a small water tower. Each tank will serve just the floors in between it and the next tank below. When the tank needs to be refilled it just draws from the tank below it. This way the building doesn’t pump all the water it needs all the way to the top floor; it only pumps water as high as it needs to go. Keeping water in a tank means it still works like a traditional gravity-fed system and should function for a while even in the event of a power outage.
Handling wastewater is relatively easier, it still just needs to flow down. The pipes just drain into one or more pipes going down to the bottom of the building.
It still has to pump it the elevation though?
Yes, but multiple tanks throughout the building means they don’t have to pump all the water all the way to the top. They only need to pump the water for the highest floors to the top.
Ah, thanks for the clarification. That makes a lot of sense.
