What force keeps water flowing through a pipe when you suck on it?

[ryanbeech]

What do you call the force that enables water to keep coming after you suck on a pipe just as long as you keep the end of the pipe lower than the water level of the source. Is it the pressure difference or is it another force.

 

[n0_3sc]

I think its called "capillary action", and its due to pressure differences.

 

[wysard]

You are correct ryanbeech. It is the pressure difference between the upper and lower ends that keeps the liquid flowing. It's called a siphon action.