There are many types of water pumps, but there is no ideal pump for every occasion. Water pumps are used mainly for dewatering purpose to reduce downtime from large rain events. Water pumps should be evaluated based on performance, low downtime, durability and price. Having a better understanding of water pumps will be important to reduce operational costs, increase the durability of your pump and the systems overall performance.
Water Pump Types
There are two general types of water pumps: centrifugal pumps and positive displacement design type. Both types follow the same purpose, which is to move water from one point to another continuously. These two major components have a wide variety of options that might be used depending on your project specific needs.
Centrifugal Water Pump
A centrifugal water pump uses a rotating impeller to move water into the pump and pressurize the discharge flow. Standard, trash and submersible models are three different alternatives to centrifugal water pumps. All liquids can be pumped using centrifugal water pumps, even liquid with low viscosity. These pumps work great with thin liquids and high flow rates.
Centrifugal Water Pump Drawbacks
Centrifugal pumps could present the following problems:
- Corrosion- Different fluid properties can corrode the pump
- Overheating- Some pump might need liquid recirculating to avoid overheating caused by low flows
- Prime- Centrifugal pumps must be filled with the fluid in order to operate properly
- Cavitation- The positive suction head of the system is too low for the selected pump
- Wear of the Impeller—Can be worsened by suspended solids
- Leakage –A long rotating shaft
Centrifugal Water Pump Uses
Centrifugal pumps are used on these applications:
- Buildings: To pump water supply, including pneumatic systems and in places where no suction lift is required.
- Boost Application- To boost pressure from the intake line.
- Wells- In domestic water supply systems
- Fire protection system - To provide a continuous pressure source, but these water pumps should be in compliance with NFPA.
- Hot-Water Circulation- To move water in a closed system which requires low head.
- Sump Pits- Either vertical or horizontal water pumps. Units are operated by an automatic switch controlled by the float.
Positive Displacement Water Pumps
Positive displacement designs are the ones which deliver a fixed amount of flow through the mechanical contraction and expansion of a flexible diaphragm. These pumps are ideal in many industries that manage high viscosity liquids, or where sensitive solids are also present. Recommended water pumps to be used for low flow and high pressure combination or other applications.
Positive Displacement Water Pump Advantages
Positive displacement water pumps or rotary pump are very efficient, due to the fact that they remove air from the lines, thus eliminating the need to bleed the air from the lines. In addition these pumps are great when dealing with high viscosity liquids.
Positive Displacement Water Pump Disadvantages
As any equipment, positive displacement water pump also present some drawbacks. These types of pumps require that the clearance between the rotating pump and the outer edge must be very close. This causes that the rotation occurs at very slow speeds; otherwise if the pump is operated at higher speed, the liquids might erode and will eventually reduce the efficiency of the water pump.