1. The problem statement, all variables and given/known data 2. Relevant equations P1 = P2 + ρgh 3. The attempt at a solution I know that only the pump at the bottom works for a very deep well, but I don't understand why the higher pump doesn't. So let's ignore the pump at the bottom and only focus on the one at the top. It works by removing air from the pipe, creating vacuum, which then "sucks" the water from the ground, like a straw. Sure. But why doesn't it work for a very deep well? If there is vacuum in the pipe, why doesn't the water goes towards it? What exactly is it that limits it from functioning for a deep well?