I can't seem to get a clear picture of how the pressure changes in liquids. Here is a small self made file, made to make myself understand this topic . Click on the attachment. Obviously as the water rose up, air pressure in the small tube rose up. (Due to Boyle's Law) Now lets assume (for the sake of better understanding) that i pushed the small tube half a meter inside the large beaker. Now what is the pressure on the yellow mark ? Is it equal to the air pressure inside the small tube, because that only makes sense. If they were not equal then there would be no Equilibrium and the water would continue to rise up/down. And, what is the pressure at the pink mark ? Is it : Pressure = Desnsity x g x h + atm = 1000*9.8*0.5 +1atm Is the pressure on both marks the same ?