In this segment of his series on the Fundamentals of Pumped Water Systems, Robert Pelikan looks at control valves of jet pumps.
This is part 2 of our jet pump series. Last month, we said that a jet pump was a centrifugal pump with a jet assembly (also called an injector), either integrally attached, as in the case of shallow well jets, or remotely attached, as in the case of deep well jets. We further explained that a shallow well jet pump draws the water up to the surface and is limited by atmospheric pressure to a depth of about 25 feet. Deep well jets, with the jet assembly located down in the well below the water level, push the water to the surface and can pump from as deep as 200 feet.
The operation of a jet pump requires a certain amount of water to be circulated back through the jet assembly as drive water. In a shallow well jet pump, the amount of water diverted is governed by the internal construction of the pump and is not adjustable because the narrow range of pumping conditions can be met without having to adjust the amount of drive water. The performance of a deep well jet pump, on the other hand, can be optimized to specific pumping conditions through the use of a control valve to create the right amount of backpressure, and this article will explain their function and how to adjust them.