How does the level of a well affect the work (Horsepower) that a water pump has to do in a lift station?

I am dealing with a centrifugal or positive displacement pump where the setpoint can be change in this case increase the well level posibly to decrease horsepower used.How does the level of a well affect the work (Horsepower) that a water pump has to do in a lift station?well, (heh),



lifting a mass m of anything a height h against the force of gravity requires an amount of energy that is equal to E = mgh, where g is the acceleration of gravity - 9.8 m/s^2.



the power comes from dividing by how long it takes to do this - power is energy / time. so P = mgh/t. that means the pump requires that much power to do so.



so, if you decrease h in the above equation, the power goes down. it is a linear relationship, so if you halve the height over which you are pumping, you halve the amount of power required.



note that this ignores the frictional nature of water, which is reasonable if the water is not moving very fast in the pump or pipes. if it is, you have a more complicated problem.