I am trying to move water using a vacuum pump. I have a vacuum pump hooked up to a tank that has one inlet, one exit with a length of hose and check valves on both. What I am doing is creating a vacuum in the tank, causing water to fill the tank. Then using the pump to generate pressure in the tank to discharge the water. I know the pressures/vacuum required to lift/push the water for my suction and discharge heights. As well as the flow rate of the pump. What I need to do is calculate the flow rate of the water into/out of the tank. My pump supplier has said to use Boyle's Law (P1V1=P2V2). The time this yeilds is close to real world results, however, in my mind it doesn't add up. It would make sense if I was moving air, but I am using the air to move water. The flow rate of the water has to be the same at both ends of the hose, as water will not compress or expand. I have since started trying to use Bernoulli's Equation (V^2/2+P/d+gZ=const), this makes more sense as it relates velocity (which leads to flow rate) to pressure. Since I am using pressure differential to move the water, I feel this is the equation I should be using. When I do all the calculations the results from Bernoulli's is way faster then the real world expermental data I have. If anyone could give any insight or a push in the right direction that would be great.