Deep-well pumps must be submersed, because while it is possible to push water up a long pipe of almost unlimited length with a powerful enough pump, pulling water up a pipe is limited to about 25 feet because of the limitations of atmospheric pressure. However, suspending a powerful pump less than 4 inches in diameter hundreds of feet underground requires special considerations and hardware to accomplish.
Pump Up
Submersible well pumps are suspended from the plastic tube that carries the water from the pump deep beneath the ground up to almost ground level, where a horizontal tube about 5 feet underground conducts the water into the household. There is a safety rope from the pump to the top of the well of about 800 lb. break strength that acts like a safety tether in the event that the pump tube breaks. Otherwise, there would be no other way to lift the pump all that distance except for the power cable, which is not designed to lift the weight of the pump.
Pitless Adapter
A pitless adapter replaces the 5-foot-deep well pit that is dug to the top of the casing so that the horizontal water tube that connects to the house can be buried at least 5 feet underground, below the frost line. This is so the water pipe can't freeze, even on the coldest of days. The pitless adapter allows the pump and pump tube assembly to be lowered and suspended from the top of the well casing into the self-sealing pitless adapter receiver slot 5 feet down the side of the casing. A special T-bar handle on a piece of 1-inch pipe connects to a blind threaded hole at the top of the pitless adapter, allowing it to be raised and lowered into place from above ground at the top of the well casing.
Electric Power
Submersible pumps are usually 230 volts AC single phase, so most require three power wires plus a ground. Two of the wires, yellow and black, are for the motor's run windings, and a third, red, also connects to the start windings to be combined with the yellow during motor starts with a start capacitor in the pump control box above ground. A pressure switch in the house on a capacity tank starts the pump usually at 30 psi and cuts it out again at 50 psi.
Replacing the Pump
Replacing a submersible pump entails connecting the lifting tool to the slide-out part of the pitless adapter and pulling the entire pump tube up along with the power cable until the pump comes to ground level, an exhausting exercise that should be done by professionals.
Precautions
Check to make sure your water table hasn't dropped significantly, or that the well isn't clogging the pump with sand. Difficult cases require the services of a professional.