Here is an intriguing question: If you have a pump rated for a maximum well depth of 8 meters and you have an infinite amount of water at 5 meters, does the pump have to work harder if you you use a 2 inch versus 1 inch down pipe? The head is the same so it seems it would be equivalent, however, if you look at the weight of water in the down pipe that the pump back flow valve has to support when the pipe is not running, the 2 inch puts a lot more force on that valve. That weight difference makes me think the pump has to work harder with the larger 2 inch down pipe. Straighten me out here if you will.