Jet well pumps with pressure switch and tank: field service manual

The motor spins an impeller; part of the discharge water is sent back through a nozzle and venturi (the ejector). That high-speed stream lowers pressure and draws more water from the suction line. On shallow-well pumps the ejector is bolted to the pump; total suction lift must stay at or below about 25 ft.

Convertible pumps can serve deeper wells by moving the ejector down the well on a pair of pipes (a pressure/drive pipe and a suction pipe, commonly 1 in and 1-1/4 in). Deep-jet setups are usually limited to roughly 70 ft or less and use a pressure control valve so the pump holds enough drive pressure; shallow setups do not use that regulator.

Suction side: one foot valve at the bottom of the suction pipe (or one check valve) holds the prime. Any air leak on the suction side, or a foot valve that leaks back, lets the line drain and the pump lose prime. A priming tee and plug at the top lets the line be refilled.

A pressure switch (often 30/50 or 40/60 psi) starts and stops the pump against a captive-air tank; precharge is set with the tank empty about 2 psi below cut-in.