How Does It Work? - Water Pumps

A water pump acts as the heart of any cooling system, circulating coolant between the engine and radiator to prevent overheating.

In simple terms, it does this via a rotating impeller which has blades to push the water through the pump, but if you want to know exactly how a water pump works, read on…

Force of nature

In order to move liquids, all pumps use a basic force of nature – as the moving pump part, be that an impeller, piston, diaphragm or whatever, begins to push or rotate, air is displaced to create a partial (low pressure) vacuum which is then filled with water.

The efficiency of any water pump is affected by atmospheric pressure. At sea level, all centrifugal pumps can lift water to a maximum of 26 feet, and the higher above sea level you go, the lower the height can be reached, dropping off at a rate of about two feet for every 1,000 feet above sea level.

Pressure is another consideration, as nature dictates that movement takes place from higher density areas, to lower density ones. This means a liquid under high pressure will move to an area of less pressure if a pathway is provided.

How does a centrifugal pump move water?  

A centrifugal pump, such as those found in car engines, works by creating a vacuum.

When the engine is started, the impeller turns and forces the water around it out of the pump’s discharge port. The partial vacuum created means water is naturally forced up the suction hose and through an inlet to replace the displaced water.

As the water hits the spinning impeller, the rotating energy is transferred to the water to force it back out – this is centrifugal force – and the process of water displacement and replacement is continued as long as the engine, and the impeller, are turning.

Looking deeper into the mechanics, in order for a water pump to create a partial vacuum, there must be water in the housing to ensure the mechanical seal is lubricated so it won’t wear out and leak. The suction hose, seal, and rings must also be in good condition to prevent air entering and affecting the vacuum.

What factors can affect the performance of a water pump?

We’ve already established how atmospheric pressure and wear and tear can affect the efficiency of a water pump, but when assessing the performance of a pump you’ll also need to factor in things like the distance water is pumped, and how many elbows and valves are present.

A longer discharge hose means water comes into contact with more hose surface, this, in turn, causes friction to build up that slows the water and decreases the discharge capacity.

Similarly, when elbows and valves are added to a pipe, they break the natural flow of the water and this turbulence creates an increase in friction that then causes a decrease in discharge capacity.

Obviously, these are general guidelines and different water pumps for different uses will all come with their own set of variables.

Want to learn more about specific types of water pumps? Click here.