Types of water pumps

Whether for home use or business, water pumps are very useful devices that serve to provide a water flow always when you need. Depending on the use of the pump, there are a few types of water pumps on the market, each with similar purpose. Some water pumps serve to bring water into a home or building, while others to bring water out. But before you search for a pump, you should know what type of pump with additional features you need.

There are only two general types of water pumps, positive displacement pump and centrifugal pump, both moving water from one point to another. Centrifugal water pumps use rotating impellers to move water, while positive displacement water pumps deliver a fixed amount of flow which makes them very effective. Below you can read a few must-know facts about both types.

Centrifugal Pumps

All pumps that use a rotating impeller to move water into the pump and pressurize the discharge flow fall in this category. Centrifugal pumps are designed to hold the water with a small valve when the water comes in for the first time, in order not to be primed again every time you turn it on. First, the water enters the pump and is being accelerated by the impeller, flowing radially towards the diffuser or volute chamber, from where it exits through it. However, some problems might appear, such as corrosion, overheating, prime, cavitation, leakage or others. These pumps find their use in construction industry, in a home-wells and in fire-protection systems for providing a continuous water flow.

Positive Displacement Pumps

Positive displacement pumps are pumps that deliver a limited amount of flow through mechanical contraction. They are perfect for many industries that deal with high viscosity liquids or where sensitive solids are present. The positive displacement pumps are versatile, have a compact design, secure a continuous flow regardless of the differential pressure and offer a high-viscosity performance. As they don't have air in the lines, the positive displacement pumps are very efficient.

Main differences between centrifugal and positive displacement pumps

If you haven't concluded the advantages and disadvantages by yourself, you can read a few differences between a centrifugal and positive displacement pumps below.

• The centrifugal pumps have varying water flow depending on pressure, while the positive displacement pumps have more or less constant water flow regardless of the pressure;
• Changes in pressure have a little effect on the positive displacement pumps, while changes in pressure have a huge effect on the centrifugal;
• The centrifugal pumps lose water flow as the viscosity goes up, while the positive displacement pumps increase the water pump;
• NPSHr in centrifugal pumps varies with flow which is determined by the pressure, while the NPSHr in positive displacement pumps varies with flow which is determined by speed;
• Centrifugal pumps perform best in the center on the curve, while positive displacement pumps on any point of the curve.