A: There are lots of different varieties of irrigation pumps. Typically, an irrigation system is going to use a pump with a relay from the irrigation controller telling it when to turn on and off and for how long for each zone it’s operating under.
Sizing that pump all depends on what kind of system it is. If it’s a residential application, it’s usually going to be a smaller pump. In municipal or a neighborhood common area, it’s going to be a larger system for multiple zones at one time.
If you’ve read any one of our blogs you know that there are all types of pumps for tons of different applications. Most pumps fall into one of two classifications based on their mechanics—centrifugal and displacement. Displacement pumps have several subcategories but are used mainly for handling high viscosity and rarely in irrigation. The one common exception is the use of fertilizer injectors, which mix fertilizer with water used in irrigation. It’s an indirect use though so, we won’t bother focusing on diaphragm pumps today.
Instead let’s talk about centrifugal pumps since they are what is used in irrigation and even then, there are many variations of centrifugal pumps.
Centrifugal Irrigation Pumps
Almost all irrigation pumps are centrifugal pumps but there are different designs within this category as well. In a centrifugal pump, an “impeller” is used to move the water rapidly in a spinning motion within the pump casing. The spinning motion moves the water through the casing by way of centrifugal force.
We could try and explain centrifugal force in scientific terms and bore you to death—but we won’t. Instead, think of those Spindletop carnival rides where you stand against the wall of a hollow cylinder. The ride spins around and then the floor drops down about five feet, but you don’t fall, you stick to the wall. That is centrifugal force at work pushing you into the wall and keeping you from falling into the middle.
Centrifugal force is an outward force away from the center of rotation of a revolving object. This force exerts its will on an external object that is rotating around that center of rotation. Centrifugal pumps work in the same manner—rotating the water very quickly and causing it to move away from the center and through the pump. The water is forced through the casing and directed to the outlet of the pump.
Centrifugal pumps may come in a “multi-stage” design which simply means they consist of multiple impellers and casings. In multi-stage pumps water is transferred from one impeller to the next with a boost in pressure. Each combination of impeller and casing is a “stage.”
Common Characteristics
Most centrifugal pumps require a “wet inlet” to operate, meaning there must be water in the inlet pipe and the casing to start. If the inlet is full of air, the pump can’t efficiently suck up water. Therefore, most centrifugal pumps must be primed before you use them the first time. However, some pumps are self-priming; usually portable ones.
Aside from common traits that all centrifugal pumps have, some distinct types have very different designs.
End-Suction Centrifugal Pumps
“End-Suction Centrifugal pumps” are the most common variation in the industry. Typically, end-suction pumps have the pump bolted directly to the drive shaft of the motor in a single unit type construction. Water enters the casing through the inlet or intake pipe located on one side of the pump and is forced out the top of the casing.
Additionally, end-suction pumps must be manually primed before first use, even ones that claim to be self-priming. Once it’s primed once it should not need priming again unless you have an intake pipe leaking a bit.
Despite the name, these pumps actually push water not suck or pull it. They are well suited as booster pumps for irrigation systems. When you install them at or below the water level they perform very efficiently. However, when trying to draw water from a water source lower than the pump, their effectiveness drops off significantly. Therefore, this type of pump is not ideal when it can’t be installed level with the water or deeper. So, contrary to their name, end-suction pumps are not efficient at sucking water upward.
Submersible Pumps
Submersible pumps are simply centrifugal pumps that are installed entirely underwater, even the motor in most cases. In these pumps, the motor is housed in a waterproof motor casing able to sustain constant submersion. Usually, a bigger submersible and motor will be built in cylindrical design. This is so it can be installed at the bottom of a water well.
Submersibles that are smaller in stature are often used in holding tanks, or sumps. Larger submersible pumps can also be installed in lakes, river streams, creeks, and bayous if the water is deep enough. Some larger submersibles can be installed on their side when water depth is an issue. However, not ALL can be installed this way so make sure to check the specs.
Submersible pumps, unlike end-suction centrifugal pumps, do not need to be primed—they’re already surrounded by water. They’re also more energy-efficient since they only push water and don’t need to suck it in as well. Most submersibles also need to be installed using a special sleeve if not installed in a water well. Even in some well installs a sleeve is required. This sleeve directs water so that it flows over the motor keeping it cool. This is especially needed in cases where the motor is exposed and not underwater or to protect the motor cord.
Turbine Pumps
A turbine pump is a centrifugal pump that is installed underwater with a motor that sits above the water and is connected with a drive shaft. Comparable to submersibles in terms of energy efficiency, they’re often used for large pump applications. These applications are unique in that the size of the motor needed would make it impossible to fit in a sleeve.
Turbine pumps often have multi-stage designs and work as a train with several engines in tandem to pull it. These are often the types you see on larger farms or municipal wells. In terms of irrigation, a common example of this are golf courses. They use them frequently to maintain the grounds using water from the hazards and other bodies of water.
Booster Pumps
You will see booster pumps in irrigation often as it helps with applications where the available water source lacks pressure. For example, your sprinkler system requires 75 PSI of pressure to work efficiently. However, the water coming from your utility company is only at 45 PSI, a booster fills in the gap by adding pressure.
A booster pump is nothing special, literally. The term simply is a label for a regular pump doing the job it’s designed to do (boost pressure). There’s nothing unique about booster pumps; most boosters are simply end-suction pumps. Simple, efficient, and affordable; they are very common in big sprinkler systems.
Are You Looking For Irrigation Pumps?
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