What is a Submersible Pump and How Does it Work?

A pump is a device that uses to transfer fluids from one location to other. There are multiple types of pumps that use in various industries all over the world. A submersible pump is a famous type of pump. It is a type of multistage centrifugal pump. A submersible pump is also known as a well pump.

What is a Submersible pump?

A submersible pump (or sub pump, electric submersible pump (ESP)) is a device which has a hermetically sealed motor tightly connected to the pump body. The whole assembly is submerged in the fluid to be pumped.

The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between the pump and the liquid surface. Submersible pumps push fluid to the surface, rather than jet pumps, which create a vacuum and rely upon atmospheric pressure.

Submersibles use pressurized fluid from the surface to drive a hydraulic motor downhole, rather than an electric motor and are used in heavy oil applications with heated water as the motive fluid.

Operating capacity

Submersible pumps come in a wide range of different sizes, determined by the particular application for which they are intended. Smaller models can be used within homes or in light commercial settings and usually have a power consumption of between.

75kw and 2.2kw, accommodating solids to a maximum of 55mm in diameter. For heavier duty applications, such as in construction and industrial applications, larger pumps are available and these can typically handle waste and solids up to 65mm.

How Do Submersible Pumps Work?

The working of the submersible pump is a little bit different than a jet pump. Because jet pumps transfer the fluid by pulling it while submersible pumps transfer the fluid by pushing it.

A submersible water pump is a machine that is linked with a completely sealed motor. It is a type of centrifugal pump. Therefore, its working is very similar to other types of centrifugal pumps. Submersible pumps submerge entirely in the water.

During the working of the submersible water pump, it pushes the water toward the surface.

As the water of well or reservoir enters into the pump by the foot valve, it strikes the impeller. An impeller is a rotatory unit that has multiple fixed blades. This impeller is connected with an electric motor through a shaft.

The impeller rotates with the rotation of the shaft. As the water strikes the blades of the impeller, the blades convert the water kinetic energy into speed and increase the speed of the water. After passing through the impeller, the water enters into the diffuser, which further transforms the speed of the water into pressure energy.

In this way, the diffuser increases desired pressure of the water; after that, pressurized water discharges through the outlet valve of the pump. In this way, submersible pumps push the water towards the surface.

Benefits of Submersible Water Pumps

There are many types of submersible pumps for many different applications, as explained in the next section. A submersible water pump’s primary benefit is that it does not suffer air leaks in the pump (called pump cavitation).

An added benefit for a deep well pump application is that you don’t need to worry about priming the well pump because the entire pump operates underwater. Submersible water pumps are also very efficient and are not subject to overheating conditions like above-water pumps.

With the exception of submersible pumps being used for permanent applications such as a pond pump or a deep well pump, smaller submersible utility pumps are portable and lightweight as well, making the pumps extremely convenient to use in hard-to-reach places or small areas like window wells.

Types of Submersible Pumps

Different types of submersible pumps are used in wells, tanks, and so on. The main classes of these pumps are discussed below.

1. Bladder Pumps

In cases where high integrity samples with low flow rates are required, and peristaltic pumping cannot be an option, the bladder pump systems offer an effective alternative to customers.

Applying a submersible stainless-steel pump and coupled controller/compressor at the well surface, the bladder pump system uses controlled air pressure to direct water samples to the surface. In addition, using a disposable polyethylene bladder within the submersible pump guarantees that air and water do not mix. Thus, a sample of high integrity is ensured.

2. Grinder Pumps

Sewage grinder pumps are created to operate with raw sewage and solid waste materials. Grinder pumps soften the solids using their cutting blades before pumping the waste.  Although on a larger scale for sewage waste, a grinder pump operates similar to a household garbage disposal. It grinds solids and other hard waste material up into fine slurry and then transfers it into the sewer system.

This type of pump is manufactured to be utilized in residential and commercial applications and high-pressure sewage systems such as long-distance pumping, high lifts, or pressurized municipal sewer lines. For direct pumping into a septic tank, the use of a sewage grinder pump is not recommended.

3. Deep Well Pumps

Deep well submersible pumps enjoy all of the benefits listed earlier, plus have the benefit of coming with a built-in check valve to ensure system pressure and prevent backflow. Plus, because these pumps are sealed and used underwater, they are virtually maintenance-free and are made with corrosion-resistant materials.

Deep well pumps can be used in well-water applications from 15′-25′ and in excess of 500′ in some situations, making them the best option for wells that are narrow or deep. Just make sure to choose the proper pump size and the correct two or three-wiring option for the application.

4. Dry Pit Submersible Pumps

Dry pit submersible pumps are initially designed for applications where the pump unit is immersed in liquid. These submersible pumps are now used in dry well stations in which the wet well and the dry pump chamber are separated. Dry pit submersible pumps have replaced the old centrifugal pumps.

5. Stainless Steel Pumps

Seemingly, stainless steel pumps have better performance than cast iron pumps. They are entirely coated with stainless steel, and thus, they have excellent acidic resistance. The whole body of the pump can be immersed in the water while running.

6. Bottom Suction Pumps

Bottom suction pumps are widely used for lake, pool, river, and mining dewatering. They are engineered with a guide sleeve beneath the pump. These pumps utilize the water from the base and effectively ensure the high-quality cooling feature of the electric motor.

These pumps are expedition and emergency pumps. The installation of bottom suction pumps is considered to be easily compared to other types of pumps.

7. Water Cooler Pumps

Water cooler submersible pumps are typically applied in water supply for the industrial, farmland, residential fields, and so on. The motor of a water cooler submersible pump can be fixed for working under the water. For cooling the hot motor, it can be filled with fresh water. These pumps are suitable in cases where high-quality water is used.

8. Oil-Filled Pumps

Despite the water-filled submersible pump being internally filled with water to cool the motor, the motor of the oil-filled submersible pump is cooled with the oil. Oil-filled pumps use oil-filled immersion motors.

These types of pumps are widely used in different areas, including water lifting in wells as well as the water supply for agricultural lands, residential regions, industrial drainage systems, and mountain areas. Oil must be filled for heated motors cooling.

These machines can be employed in cool areas since oil cannot be frozen. The fitting and refurbishing of these pumps are very simple. These pumps transfer the clean water such as the lakes, pools, or rivers.

Although these pumps have longer service life than water-filled submersible pumps, these pumps may have an environmental impact due to oil pollution. Moreover, under the same flow conditions, they are more expensive than water-filled submersible pumps.

9. Borehole Pumps

Borehole pumps are centrifugal pumps operated by a submersible motor. Because they typically draw into the fluid directly without a suction line, they need to be constantly submerged in the fluid.

These pumps are engineered as single- or multistage pumps coupled to the submersible motor. Depending on the application, the motor can be located above or under the pump.

Submersible borehole pumps are employed in tank farms and as cavern pumps. Borehole pumps are more cost-effective than deep-well pumps, particularly for deep installations due to their simpler designs.

10. Utility Pumps

Submersible utility pumps can remove standing water, empty clogged sinks, or drain window wells, and much more. When choosing a utility pump, the most important factor to consider is portability. Utility pumps are best used in small spaces where other water pumps just won’t fit.

The inlet size on the pump will tell you how quickly you can pump the water through the pump and discharge it elsewhere. A utility pump with a float switch (pictured below) is great too because they automate the pump by turning it on and off when water levels change, so you don’t have to watch it while it works.

Urgent and semi-regular pumping applications are perfect for utility pumps, as long as the water doesn’t have debris or solids in it. Utility pumps are not meant to pump solid items at all, so don’t use one for cleaning dirty water with solids, and especially don’t use this pump for sewage-type applications.

11. Solids Handling Submersible Pumps

These submersible pumps are able to transport solid material through the pump without any obstruction or interference from entry to discharge. Spherical material with a diameter of 2 inches to 13 inches or more can move through these submersible pumps.

12. Booster Pumps

Booster pumps raise the low flow of the water in systems or industrial facilities and transfer the water from a lake, pond, or storage tank for domestic or commercial use. For example, a household that does not receive adequate pressure from the city water source needs a pump to increase the low pressure of the water flow. A hotel requires a large commercial booster pump to bring water to the top floors.

A booster pump is also applied to re-pressurize water from a storage tank and transfer it throughout a home. For example, in a rain harvesting system, water accumulates in a storage tank. To use it for flushing toilets or washing laundry, the water needs to be transferred from the tank into the house.

13. Condensate Pumps

A condensate pump is a centrifugal pump used in condensers to transfer the condensed steam as water (called condensate) in a vacuum (near vapor pressure). In an open circuit, the condensate pump moves the condensate into a tank (feed water tank). However, it sends the condensate into the boiler feed pump through a low-pressure feed heater in a closed circuit.

14. Macerator Pump

A macerator pump is connected to a toilet that grinds up solid waste utilizing a high-speed rotational blade. It then pumps the waste into the sewerage system.

Macerators are created to pump out the waste materials and wastewater from toilets without relying on a regular drainage system. Usually, they are used in bathrooms that are far from the main drainage systems.

Submersible Pump Applications

Submersible pumps are used in these industries: drainage, slurry pumping, sewage pumping, water wells, oil wells, seawater handling, sewage treatment, firefighting, deep well drilling, irrigation, mine dewatering, artificial lifts, and offshore drilling rigs.

One of the main benefits of a submersible pump is that it can be positioned below ground level without causing any access issues. They are thus installed in a range of environments, including:

• Deep wells
• Areas that are prone to flooding
• Where a traditional pump motor could become damaged by contaminated water
• Settings where a quiet pump is necessary
• Where there is limited space
• Agricultural applications

Inappropriate applications

Whilst submersible pumps have a wide range of uses, there are some instances where they are not an appropriate choice. These include:

• Where the liquid temperature is excessively high
• If the environment is particularly corrosive
• Where there are a significant number of abrasive elements
• Where the fluid contains solids or contaminants of an excessive diameter

Do’s & Don’ts of Domestic Submersible Pumps

For additional guidance, the team at Anchor Pumps has put together a useful list of submersible pumps dos and don’ts to assure safe operation and installation of domestic submersible pumps.

Do read thoroughly all installation information in the manual provided.

DO:

• Do check the pump to make sure it isn’t damaged prior to use.
• Do read thoroughly all installation information in the manual provided.
• Do check the voltage of the pump
• Do check the size of the sump, so the float switch can freely operate
• Do connect to an appropriately protected power supply
• Do make a note of the pump type before fitting in sump – easier if pump fails and is underwater.
• Do try not to place the pump on the bottom of the sump but slightly raised to reduce the chance of the filter blocking
• Do fit a NRV if possible, don’t make the pump work harder than it needs to
• Do make sure the float switch can move unrestricted
• Do make sure the pump filter is cleaned regularly

DON’T:

• Don’t lower the pump down with the power cable
• Don’t fit smaller discharge hose than the pump connection
• Don’t allow water to freeze around the pump
• Don’t allow heavy objects to fall on top of the pump or stop the float switch from operating
• Don’t leave the top of the sump open or uncovered
• Don’t lie the pump on its side
• Don’t work or move the pump whilst it is connected to the power supply
• Don’t use the pump to empty swimming pool water if people are in it
• Don’t use the pumps for pumping hydrocarbons (petrol, diesel, fuel oils, etc)
• Don’t allow the pump to run dry

If in doubt ring your supplier and ask for advice, good suppliers will always have a technical support team.

Advantages of Submersible Pumps

The submersible pump offers several major advantages over other types of pumps:

• Priming: They don’t have to be primed. They are self-priming because they operate below the surface of the fluid being pumped.
• Cavitation: Because they are fully submerged, submersible pumps are not prone to cavitation. This can be a problem with centrifugal pumps and other types of positive displacement pumps.
• Efficiency: When a pump is submerged there is positive fluid pressure at the inlet of the pump. This condition can increase efficiency due to less energy required to move fluid through the liquid path of the pump.
• Noise: Being submerged, these pumps are very quiet in most applications.

Disadvantages of Submersible pumps

There are also some disadvantages to contend with:

• Accessibility: Submersible pumps are often not easily accessible for routine inspection or maintenance, especially in deep well applications. This makes it difficult to perform preventative maintenance and in many applications pumps are left to run until they break down and need to be replaced.
• Corrosion: Prolonged exposure to a liquid of any sort will lead to corrosion. Submersible pumps are often used to handle liquids that are corrosive and abrasive. Seals are especially prone to corrosion, which leads to leaks and damage to the motor. To counteract corrosion these pumps need to be made of corrosion-resistant material, which can make them more expensive than other types of pumps of the same capacity.

Buying a submersible pump: four tips

If you are looking for a submersible pump and want to make sure it is worth the investment, the following four tips may come in handy for determining the best model:

Tip 1: Check pump capacity. One pump may have a capacity of 7,500 litres per hour, while another one is able to process 18,000 liters per hour. Ask yourself what capacity you require and look for a pump with this capacity.

Tip 2: Check the delivery head. The delivery head refers to the maximum height at which a pump can raise water.  Some pumps have a delivery head of eight meters, while others have one of five meters. Check again what you need and find a pump that meets your requirements.

Tip 3: Consider whether the pump needs to switch on and off automatically. This is done with a float. In automatic mode, pumps are not capable of pumping a surface completely dry. This is only possible in manual mode, and you need to switch it off in time.

Tip 4: Check which accessories are supplied with the pump. Some pumps are more user friendly than others, simply because they come with more accessories. If you consider ease of handling very important, we advise you to check which accessories are standard with the pump.

With the above tips in mind, you will find the submersible pump most suitable for your needs.

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