Watz ur Wattage ?

Herez a puzzle:

I hope every1 has seen those water sprinklers spraying water in a garden. Nice little things they are, for they rotate by themselves throwing water around! Its obvious that laws of momentum conservation are the secret behind the working of this interesting gadget. But here comes the catch. Imagine that water is not made to gush out of the sprinkler. Instead, it is dipped in a tank and by some means, water is made to flow inside it. There can be 2 such possibilities :

• The pressure outside is increased
• The pressure inside the pipe is decreased.

The question now is ... is water flows as shown in the figure, which way would the sprinkler rotate ? ( Aniclockwise or clockwise ? )

Plz don't post you answers here, email them to twishmay@gmail.com with a satisfactory explanation.

~ Twish ~