Executive summary. There are different ways to prime a water pump. Here is one way you can do it using compressed air and the Venturi effect. And yes, a Venturi eductor is similar to an ejector!
What is meant by priming a pump? Look at Figure 1 below. This is a schematic elevation view of a pump on a concrete pad. Notice that the pump’s suction side is dry (the water level at the source is below the suction side of the pump – this results in an ‘air gap’ between the suction end of the pump and the water level in our tank). This is a problem for a centrifugal pump because as the pump impeller spins and is looking to suck in water, it only “sees” air. This pump cannot pump air.
The solution is to prime it – to introduce water to the pump. If we bring water to the pump, the pump impeller can do what it’s designed to do: move water.
Figure 1. Pump in need of a prime due to the air gap.
Let’s prime it using a Venturi eductor. Since we have the condition shown in Figure 1, we must find a way to move water to our pump. We introduce the Venturi eductor which uses difference in air pressure to bring the water to the pump. Read steps 1 through 6 in Figure 2 which explain how the phenomenon of the Venturi Effect, through the creation of differential pressure, moves the water vertically through the pipe.
Figure 2. The Venturi eductor and the Venturi Effect.
Figure 3. The Venturi eductor in place.
My story. Construction, when done strictly by the book, is simply building what is shown on a piece of paper (or a digital PDF). It’s no thinking, no ingenuity, and then a high potential of good deeds resulting in punishment (there’s another article by me somewhere about ‘no good deed going unpunished’). Anyway, when you get a smart contractor who is solution-driven, they find ways to solving problems. This recently happened where an air gap existed and the pump had to work. So, in came the eductor. This resulted in water through the pump. Voila!
Great job contractor!
Work safe!
