Contractors need to seek out workers who have some idea about the kinds of work they will be doing, who are trainable, have good communications skills so they can talk to customers and contractors, and be able to write legible reports that wil be acceptable if they are ever used as evidence in a court case.
Logic states if you have the same amount of air available to push the water out, you will be able to deliver the same amount of water between the pump cycles regardless whether the tank has a diaphragm separating the air from the water.