water tanks heigt, really necessary for pressure?

[BauTomTom]

Hi

I wonder why the watertanks needs to be so high. Don't you get the same pressure when you tank is just low and only one small tank is placed in the right height to create the necessary pressure?

Then the whole tower structure could be much more lighter

See attached sketch

And, is it also not possible to reduce the pipesize by increasind the tank height?

see attached sketch

BauTomTom

 

[wardak21]

Hello,
Regarding your question, i can say that the water contained in the tank is for use, and it is going to reduce when water is using. when amount of water spill out more than the volume of the small thank considered for producing pressure the water level will go down fast and before starting the water-pump we will have no pressure in our water supply network.

Respects

Halim

 

[csd72]

BauTomtom,

I expect it is because of the cost of the supporting structure. Yes, as far as the tank walls are concerned, a lower wider tank exerts less pressure and therefore reduces the ring tension.

But you also have to consider the cost of the supporting columns that would need to support it both vertically and laterally and the cost of the beams required to support the larger base.

Tension is by far the cheapest type of force to design for.

 

[Ron]

It's a trade-off. Ground storage tanks require more pumps to develop the required water pressure and distribution. They only work when there's electricity, engines, or a generator. Elevated storage tanks, though a bit more costly to build and maintain, require smaller distribution pumps and can at least provide some water even when there is no power to their booster pumps. Gravity is free.

Small volume, elevated auxiliary tanks to provide pressure, in conjunction with larger ground storage tanks have not been popular in the US for a variety of reasons.

To give you an idea of the pressure differences, a typical ground storage tank will provide a little less than 10 psi water pressure at its base. An elevated storage tank, say 120 feet high, will provide close to 50 psi water pressure at its base.

 

[JStephen]

The elevated tank is just a means of storing water at pressure. In a typical installation, both elevated and ground storage tanks are used, with sizes adjusted as needed. An alternative for smaller installations is a hydropneumatic tank.

 

[MiketheEngineer]

That is why most cities have elevated tanks. Fill the tanks at night when electricity is (used to be) cheaper and let them drain all day. Repeat.

 

[paddingtongreen]

In your scheme, the upper tank would not have sufficient water to last the day, then the pressure would drop drastically. Additionally, you would have to design the lower tank for the full head, much greater pressure than the normal arrangement.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[BauTomTom]

---to wardak---
I think this is the main reason. That the much more smaller volume would be used to quick. But it could be designed for the top usage of the day ad the rest of the day could be covered with the lower pressure (from the lower tank) maybe?

---to csd72---
You are right. The whole issu is the structure for the main tank. Why do we need to build a huge tower where the 20 000 liter would be placed. I thought maybe it would be efficient enough to shift only 1000 liter so high and keep the rest lower since the 20 000 liter shall cover the whole week only.

---to JStephen—
This is what I mean “is just a means of storing water at pressure…..In a typical installation, both elevated and ground storage tanks are used, with sizes adjusted as needed”