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The More You Know: How Does a Pump Work?

Whether you are a single-family home owner or the manager of a New York City apartment building, you probably have at least one pump on your property. If you’ve ever wondered, “How does a pump work?”, this post explains the mechanism to you. Once you understand how pumps function, you can perform more troubleshooting on your own or better explain problems when you contact experts like Antler Pumps for a service call.

Positive Displacement Pumps: The Basics

Moving fluid through pressure changes

Positive displacement pumps are one of two common pump types used in buildings. The other type of pump is called a centrifugal pump, which we’ll discuss below.

Positive displacement pumps all execute the same essential function: moving fluids. They usually move liquids like water. The main moving part of the pump pushes air out of the way, creating a vacuum into which the substance being moved flows.

The process repeats itself over and over again, continuing to push the fluid from the inlet side of the pump (the entrance, or suction side) to the outlet (the exit, AKA the discharge side). The moving part of the pump that displaces fluid may be a flexible diaphragm, screw, or piston.

While pumps before the Industrial Age were hand cranked, most pumps today use a motor to drive the motion inside. Electric motors are most common, but you’ll also find pumps powered by steam, hydraulics, and internal combustion, among other sources.

To understand pump physics, think of using a drinking straw. When you suck on the straw, you create a partial vacuum in your mouth and decrease the pressure within the straw. This pulls liquid up the straw because there is a difference in pressure between your mouth and the pressure in the liquid you are drinking.

Centrifugal Pumps: A Different Mechanism

Harnessing centrifugal force

Centrifugal pumps utilize an alternate mechanism for moving fluids: centrifugal force. An impeller inside the pump spins around, moving water from the inlet side to the outlet side of the device. Impellers look like fans with blades or vanes that rotate very quickly. The rapid spinning of the impeller creates centrifugal force, which pushes the fluid through the pump.

It’s easy to confuse centrifugal force with centripetal force. As a refresher, remember that centrifugal force is an outward force felt in a rotating frame of reference. You may have seen centrifuges spinning blood in a laboratory to separate its components by density.

You might have also used a salad spinner that removes water from rinsed lettuce by moving it quickly around in a circle as you crank the handle. Centrifugal force removes the water by forcing it to the outside part of the spinner, while the lettuce remains dry in the center basket. The same thing happens in your clothes washer on the spin cycle.

An even more familiar example is the pull you feel to the left when you make a sharp right turn in your automobile. You can really notice this on some curved exit ramps when driving off the highway. Some amusement park rides take this sensation to extremes.

There are two basic types of pump impellers:

• Axial flow: moves fluid parallel to the shaft
• Radial flow: moves fluid perpendicular to the shaft

Sometimes impellers are completely open inside the pump casing. At other times, they are covered on one side or completely covered (AKA shrouded), depending on the pump’s intended function. Like positive displacement pumps, centrifugal pumps use a motor to drive the impeller.

Other Pump Parts Essential to Function

Parts for control, safety and efficiency

Depending on the pump you’re using, you’ll find other parts that are vital to its function:

• Casing: protects the pump from the outside environment and protects users from getting caught in the inner mechanics
• Shaft: transfers power from the driver to the element that moves the liquid and can be used to change the speed of the pump
• Bearings: rollers, balls, or sleeves used to reduce friction
• Strainers: catch debris or unwanted material before they enter the pump
• Gaskets and seals: prevent material from leaking outside the pump and keep the interior of the pump clean
• Valves: help control the flow of liquid inside the pump
• Mounting: parts that affix the pump to one location and reduce vibration

The next time you’re having a pump serviced on your property, ask if you can observe. You’ll learn more about what type of pump is operating and what the interior components look like. This will help you if you have a problem with the pump in the future.

Do you have a pump that doesn’t seem to be working right? At Antler Pumps, our professionals have decades of experience with all types of residential and commercial pumps. Feel free to get in touch with questions by calling us at 212-534-2500, or use our online form to schedule an appointment.