Pump Types

Overview

Pumps are the most common and inexpensive way to lift, move, and pressurize water. Pumps lift water from water sources to storage tanks at higher elevations and pressurize water systems to deliver water to the place where livestock will use it.

Advantages

  • Modest initial cost and reasonably long life.
  • Require little maintenance except for piston or reciprocating pumps.
  • Simple and easy to understand how to use.
  • Pumps located above ground can easily be replaced with available tools.
  • Powered by electric motors or gas engines.
  • Available in a wide range of sizes and manufacturers.
  • Electrical pumps are easily automated, even at remote sites.

Limitations

  • Desired flow and pressure rates determine the type of pump needed.
  • Pumps incorrectly matched to the application may be inefficient or fail to work.
  • Engine-powered pumps must be checked daily.
  • A controller specific to the application is needed to operate an electric pump.
  • When extracting a pump installed in a deep well for maintenance, special equipment may be required.

Design Considerations

The two broad classes of water pumps are centrifugal (turbine) and positive displacement. Air-lift pumps are a third type of pump that uses compressed air. Each type of pump has specific properties that make it best suited for a specific set of conditions.

Centrifugal pumps are not complicated, operate smoothly, are efficient, affordable, and have a long life. Centrifugal pumps have large impellers that spin to move water by suction and are not powerful enough for most wells. Centrifugal pumps are commonly used to move or pressurize water from shallow wells (less than 24 feet to water) and are installed above ground. To avoid the need to prime the pump with each use, a check valve is essential.

Jet and deep well jet pumps are generally used in shallow wells with static water levels greater than 25 feet. A jet pump consists of a centrifugal pump with a jet assembly inside the well to create a low-pressure zone that lifts water from the well. With the jet, water can be lifted about 100 feet. The greater the lift to the pump intake, the more water is required to power the jet, reducing the discharge rate. While jet pumps are considered less efficient, they are generally adequate for intermittent livestock watering. All major parts of a jet pump are at the surface, facilitating maintenance, but require a pump house to avoid freezing. This style pump is frequently upgraded to a submersible centrifugal pump when replacement is needed (eliminating priming issues).

Submersible turbine pumps are efficient, have a long life, low operating costs, and are frequently used in small water wells. Designs are available for a wide range of flow and pressure applications. The pump has small impellers that easily fit inside the well casing. Each impeller has limited pressure and flow capacity. By using multiple impellers in series along a common shaft, sufficient head pressure is developed. Submersible pumps are constructed with the motor at the bottom, impellers and discharge at the top, and the intake located between the motor and impellers. Waterproof wires deliver electricity down inside the well casing to power the motor.

Diaphragm (positive displacement) pumps are simple in design. They are often paired with a solar power supply. An off-center cam or knob on top of the drive shaft moves a diaphragm up and down to produce a pulsating discharge. A check valve on the intake side of the pump allows water to enter the pump but not to flow backwards. A second check valve on the outlet side allows water to exit the pump but not reenter. Submersible diaphragm pumps can raise water as much as 200 feet. Diaphragm pumps placed on the surface are limited in their lift but can generate adequate pressure for use with livestock watering.

Piston and reciprocating pumps use a piston or plunger that produces a pulsating discharge. Windmills most often use a piston pump that is in the water below the rotor. Check valves located on the intake and piston keep water from flowing backward. Piston pumps are easily adapted to hand- or machine-powered operation. Continuous flow pumps are well suited to pairing with electrical power and have often replaced piston pumps. In remote locations where electricity is not available, the continuous flow pump is still used with windmills, as it was used historically.Maintenance of moving parts is relatively greater for piston pumps. Reciprocating pumps are usually paired with an electric or gasoline motor and can be used for very high lifts.

Helical pumps are comprised of only two parts: a rotor inside a rubber stator (sleeve). As the corkscrew rotor turns, it forms cavities within the stator that move the water through the pump. Suitable for deep wells, helical pumps can move relatively small amounts of water to very high heads. Helical pumps are easily damaged by sand or other debris. Repairs are relatively easy and inexpensive. These helical pumps can create higher heads than most other pump systems.

Variable speed pumps or variable frequency drives (VFD) have a control box on the motor that reduces the number of times the pump cycles by adjusting the motor speed to meet the current water need rather than maximize water production. Reducing frequent start/stop cycles can lengthen the life of a pump motor. The variable frequency drive allows use of a smaller pressure tank. A pressure sensor mounted on the pump outlet measures water pipeline pressure and communicates with the variable frequency drives to adjust the motor speed to keep water pressure constant as the rate of water draining from the system varies. At usage rates of less than 1 gallon per minute, the pump shuts off until water pressure drops and the variable frequency drives restarts the pump. Most variable frequency drive systems include a “soft start” feature that allows 2 to 3 seconds for the pump to start, rather than the standard pressure switch-activated motor which restarts within a fraction of a second.