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# Pressure of water spraying out of leaking tank

## Pressure of water spraying out of leaking tank

(OP)
Hi guys,

I have aquestion regarding the spraying pressure of a water tank.
Suppose I have a storage tank for water with the following parameters:
Height: 10 m
Capacity: 651900 liters

There is a hole on the tank shell, almost at the bottom of the tank (assume that it is at the bottom) and the hole hase a diameter of approximately 11 mm.

What would be the pressure of the water spraying out at that depth?

What I know so far, is the hydrostatic pressure at that depth in the tank, which is 14.2 psi.
But the pressure increases when it is sent through the small hole right?
Can I apply Bernoulli's formula to calculate the pressure of the water spraying out?
I'm not sure. And even if I could use that, I don't have any speeds of fluid.

Any ideas?

### RE: Pressure of water spraying out of leaking tank

I recommend you obtain Crane Technical Paper No. 410, it is an excellent reference.

Crane Technical Paper No. 410

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

### RE: Pressure of water spraying out of leaking tank

Pressure inside the tank is hydrostatic pressure, as you have pointed out. Pressure outside the tank is atmospheric - it is and it will always be. This applies for the surrounding air, flue gases, and as well for water jets released from storage tanks.

What happens during flow of water from inside the tank through a nozzle (or hole) is that hydrostatic pressure of water converts into velocity of water jet plus the loss of energy required to overcome friction losses. You can observe this pressure/velocity dependence and conversion if you drill a hole at several different elevations of the tank. The hole at the lowest elevation point will have the highest jet velocity, because at that elevation the hydrostatic pressure is the highest for all of the selected elevation points.

If you use Bernoulli equation, you can calculate jet velocity because the pressure is known - not the other way round.

Dejan IVANOVIC
Process Engineer, MSChE

### RE: Pressure of water spraying out of leaking tank

(OP)
Thank you all.
@EmmanuelTop, thank you! That was what was confusing me. But I got it now. Thanks again.

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