Negative absolute pressure? How it can be? - AUTOSOLVED

[Zucca]

Guys,

I am was doing something wrong but I don't know where. It's a very simple physics problem.

 

I have a bucket on the ground full of water. On the water surface there is 1 Bar of atmosferic pressure.
Now I take a 20meter pipe open in one end and I fill it with water.

Now I submerge the open pipe end in the bucket and I keep the 20 meter pipe full of water vertical.

Let's think about the hydrostatic pressure in the pipe.

10meter water are 1 bar, so at the 10 meter high I have 0 bar absolute. But if I move higher I go negative?

What is the absolute pressure on the top of the pipe?

-1 Bar? So below the vacuum, ehh?

ahh while I was writing it I got it...



In a static condition the pressure difference of 20meter water top-bottom are 2 bar.
The 1 bar on the bucket water surface can't keep op with the 2 bar of the water.... so at equilibrium I have th e first 10meter pipe full of water and the rest is vacuum.
Basically when I submerge the pipe, I create an atmosferic barometer... because the 10meter water on the top flows down in the bucket creating vacuum.

Sorry for posting this but I had already almost written it up.

 


 

[tautech]

 
I think any of us that have been around here for a while have deleted a post/thread just before posting as after proof reading we see what was staring us in the face and we couldn't damn well see it. 
I know I have. 

As they say sometimes; one can't see the wood for the trees !

When it happens, don't ya just feel like doing this:     

[NiHaoMike]

Once the pressure goes below the boiling point of the water at its current temperature, the water will boil.

[Zucca]

Mike, I was going to post that. So I assume above water it's not vacuum but H2O vapour.

Dammm it... it's just a bucket and a pipe. How can it be so complicated....