How Does a Well Pump Work?

Many of us who rely on well water for our homes and businesses might not actually know the basic principles behind how these essential machines function. The basic principle is one that is easy to comprehend.

If you think of your well pump as a very long straw, then you can picture how suction is used to lift water to the surface. When drinking through a straw you use your lungs to pull the air from your mouth. This creates a tiny vacuum in your mouth that is quickly filled by liquid from the straw being pulled up from your margarita. Oh, yes, this is important: you're drinking a margarita in this scenario.

A well operates similarly. Using a pump (instead of your mouth) a vacuum is created and the pressure at the top of the well is lower than that at the bottom where the water is. The pressure we are referring to in this case is atmospheric pressure. Think of a column of air stretching from the soil to the top of the sky. Even though air feels weightless the weight of all that air at the surface is 14.7lbs! Any reduction in that pressure, for example like the lower pressure area created by a vacuum, causes the contents of high pressure areas to move to fill the vacuum.

The hand-pump diagram makes this concept easy to see. When the piston is raised you can see a space created between the piston and the top of the water suction line. This space is a vacuum, and the pressure in the water suction line is higher than the low-pressure vacuum created by the lifting piston. When the piston is plunged again a one-way check valve closes at the top of the well and drives the water through the outlet. This functions the opposite of a low-pressure vacuum, it becomes a high-pressure compartment forcing the water to seek the area of low pressure outside of the pump.

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