Shallow-Well Jet Pump

Overview

A shallow-well jet pump lifts water from a well or cistern up to about 25 feet below the pump and pressurizes it for household use. Unlike a submersible, it sits above ground and pulls water up by suction, which is what limits its depth: at sea level atmospheric pressure can only support a column of water so tall. To stretch that suction it uses a jet ejector, an old but clever trick that recirculates some of its own discharge to boost the lift at the well intake.

The Drive Motor spins the wet end through a Shaft Seal that keeps water out of the bearings. The Hydraulic End section holds the impeller, diffuser and ejector; it sits inside the cast Pump Body. A Pressure Switch cycles the motor to hold pressure, the Priming Assembly parts keep the pump filled, and the Electrical Set set supplies and starts the motor.

How it works

The motor drives the Impeller, which throws water outward into the Diffuser and builds pressure. Part of that pressurized water is sent back down through the Ejector Nozzle into the Venturi. As the jet squeezes through the narrow throat it speeds up and its pressure drops, creating suction that drags fresh well water up the intake pipe. The lifted water and the drive water recombine and pass through the impeller again, so the ejector effectively multiplies the suction the impeller alone could produce.

Before first use the casing must be filled through the Priming Plug; the Check Valve then holds that water so the pump does not lose prime when it stops. The Pressure Switch watches system pressure with a Pressure Sensor and snaps the motor off at the cut-out setting and back on when a tap drops the pressure, so the pump runs only as the house draws water. The Start Capacitor gives the single-phase motor the torque to start under load, and the Shaft Seal protects the Ball Bearing pair from the pumped water.