How much pressure needed to pump the water from the closed well?
It is quite right that it depends on the pressure inside the closed well but there are other factors too. You have to understand NPSH available as well as NPSH required. Otherwise multistage submersible pump will draw the water from deep well. NPSH parameter shows the difference between the actual pressure of a liquid in a pipeline and the liquid’s vapor pressure at a given temperature. NPSH is an important parameter to take into account when designing a circuit: whenever the liquid pressure drops below the vapor pressure, liquid boiling occurs, and the final effect will be cavitation: vapor bubbles may reduce or stop the liquid flow.
