Do they really store drinking water? Are they used to store water for fighting fires? It seems impractical to store basically a drum of water hundreds of feet in the air.
In: Engineering
The purpose isnt necessarily to store water, but to pressurise it.
Water flows downhill. This means that is you have a reservoir of water up on a hill feeding houses down in the valley below, gravity will cause the water to flow from the reservoir to the houses, and have enough pressure at the end to flow out of of taps.
This is a problem if you live somewhere very flat – if your water supply is at the same level as your end user, there is now no drop in height to create that flow, and we need to do it artificially.
You could just attach a pump to your water supply to push the water through and pressurise it, but water use isn’t predictable – you would need a way to have a big pump running when lots of people need water, but somehow also turn it right down when only a few people are running taps. At the moment we just don’t have a way to adequately detect and pressurise a system quick enough for this to work.
The answer is the water tower. To create a nice consistent pressure, we want a change in altitude between the supply and end user, so we can just make that ourselves by lifting the water supply up into the air. The water is up high, and as it flows down the pipework to the houses below it creates a suitable head of pressure.
Because it is a big tank up in the air we do need to pump water up there to fill it, but rather than needing to do this continually and vary the pump to match the demand, we can just pump up water when the tank gets below a certain level, turn it off when the tank is full, and then let the tank empty as it is used – turning the pump back on when the level drops again. This is a much simpler system as we just need to turn the pump on/off to fill a tank, rather than trying to vary it to match demand.
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