How do you sample from deep wells with increased pressure?

Deep wells do use higher air pressure to drive the pump. In the case of a standard bladder pump, if the pump is downwell about 1,000 feet it will need up to 500 psi of air pressure. If you use something called an extended inlet tube or a drop tube inlet, you can actually put the pump at a higher point in the water column and then put the intake lower in the well. Using this methodology, QED has successfully sampled at about a 1,700 foot depth.