Water jet eductors also known as venturi eductors, utilize the kinetic energy of one liquid to cause the flow of another. Eductors consist of a converging nozzle, a body and a diffuser and resemble syphons in appearance. In operation, the pressure energy of the motive liquid is converted to velocity energy by the converging nozzle. The high velocity liquid flow then entrains the suction liquid. Complete mixing of the motive and suction is performed in the body and diffuser section. The mixture of liquids is then converted back to an intermediate pressure after passing through the diffuser.

There are three connections common to all venturi eductors.

(1) Eductor MOTIVE Connection: This connection is where the power for the eductor is generated, by increasing the velocity of the motive fluid. The Jacoby-Tarbox eductor nozzle in this section takes advantage of the physical properties of the motive fluid. Eductors with liquid motives use a converging nozzle as liquids are not generally compressible. Eductors with gas motives utilize converging-diverging nozzles to achieve maximum benefit from the compressibility of the gas. All Jacoby-Tarbox eductor nozzles for eductors have smooth flow paths. Flow paths with sudden steps or roughness on these high velocity surfaces cause eductors to operate less efficiently.

(2) SUCTION Connection: This connection of the eductor is where the pumping action of the eductor takes place. The motive fluid passes through the suction chamber, entraining the suction fluid as it passes. The friction between the fluids causes the chamber to be evacuated. This allows pressure in the suction vessel to push additional fluid into the suction connection of the eductor. The high velocity of the motive stream in this section of the eductor directs the combined fluids toward the outlet section of the eductor.

(3) OUTLET Connection: As the motive fluid entrains the suction fluid, part of the kinetic energy of the motive fluid is imparted to the suction fluid. This allows the resulting mixture to discharge at an intermediate pressure. The percentage of the motive pressure that can be recovered is dependent upon the ratio of motive flow to suction flow and the amount of suction pressure pulled on the suction port. The mixture then passes through the diverging taper that converts the kinetic energy back to pressure. The combined fluid then leaves the outlet.