Wow! Seems like such a simple question but I think it might require a complicated answer.

This site http://www.engineeringtoolbox.com/dy...re-d_1037.html can get you close but you've got to know density. This wiki site http://en.wikipedia.org/wiki/Density has a chart that shows water density at temperature.

So if you subsitute the fluid density p(rho) with the equation m/V your equation would be pd = 1/2 (m/V) v2. Solving for velocity would be, well I can't figure out how to write that here but you get the idea. What all this is trying to say is you'll have to get temperature somewhere.

I agree with all in that I'd like to see how you solve this problem.