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Comment by rgmerk | Hacker News Reader

One minor but interesting exception - farmers have historically often put domestic water tanks on top of towers to ensure even water pressure. Direct pumping leads to cycles where the pressure in the system rises and falls as the pump cycles on and off, which is very unpleasant if you’re trying to take a shower!

I believe modern off-grid home water pumps use more sophisticated motor control to avoid the need for the raised tank.

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Off-grid domestic water uses tanks fitted with rubber bladders that keep the water at a roughly constant pressure and reduce the frequency the pump has to cycle.

That's not an exception, that's an entirely different use for a raised tank. And not a very big one either.

It depends what you're calling "not a very big one". On our farm we have a 5000 litre galvanised high tank for house-water.

Right, but do you need more than 50 of those for the specific purpose of evening out pressure?

I'd say it's a quite big one, "every city" has water towers to provide pressure to the people living in it, or they rely on the water source if it's higher up than the city.

There are probably exceptions, where this isn't true, but raised tanks make modern society possible.

https://youtu.be/yZwfcMSDBHs more on water towers, which are raised tanks of water.

We also pump water into fake lakes to later extract electricity from it. (https://youtu.be/66YRCjkxIcg)

Another good thing with water towers is that we can keep running the pumps at a lower RPM where efficiency than if we were trying to build a system with pumps to keep pressure.

Great channel if you're curious about everything related to humans relationship with water.

> I'd say it's a quite big one, "every city" has water towers

I meant not a big tank is needed for one house. I wasn't talking about the size of the use case.

> We also pump water into fake lakes to later extract electricity from it.

We do, because lakes are much much bigger than tanks on a house.

I thought the point of water tanks is that one needs a simpler / weaker pump to maintain the water pressure.

i.e. if you want to maintain water pressure X, with a pump you need something that can push X, but with a tower, you just need a pump that can keep the tower full over the course of a more length period and just has to pump at the average of what it takes to keep it full over the course of that longer period (i.e. the average pressure needed to maintain the tower is less than the pressure you need to provide).

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