# Water tower

1. Oct 16, 2007

### yuvlevental

A water tower, vented to the atmosphere, is drained by a pipe that extends to the ground. The top surface of the water in the tank is 13.3 m above the ground. If the valve in the drain pipe is closed, what is the absolute pressure in the drain pipe at ground level?
2.32×105 Pa

If the valve is now open and the cross-sectional area of the drain pipe is 1.69E-2 m2, find the volume flow rate in the drain pipe. Assume that the water speed at the top of the water in the tank is negligible.

Are the pressures at top and bottom the same when the drain is open?

.5*1000*(v1^2)=1000*-9.8*13.3

v1*1.69E-2=volume flow rate

Am I right?

2. Oct 16, 2007

### Pyrrhus

Hello, is the drain pipe directed vertical from the center of the tank to ground level?

3. Oct 16, 2007

### yuvlevental

the drain pipe starts at ground level and goes under

4. Oct 16, 2007

### Pyrrhus

so ground level is the bottom of the tank?

What's the tank's height?

5. Oct 16, 2007

### yuvlevental

13.3m, yes, ground level is the bottom of the tank

6. Oct 16, 2007

### Pyrrhus

Well if the tank is open both at the top and the bottom, what do you think the pressure will be? both are open to the atmosphere in said points.

7. Oct 16, 2007

### yuvlevental

both pressures would be the same, because both points are exposed to the atmosphere. So is the rest correct?

8. Oct 16, 2007

### Pyrrhus

Yes, the same.

The rest is right.

You need to apply Bernoulli equation at the top of the tank and at the drain pipe.

Last edited: Oct 16, 2007