A submersible well pump is a multistage centrifugal pump coupled directly to a sealed submersible motor. The complete unit operates below the water level inside a well or borehole and pushes groundwater to the surface through a discharge pipe.
In a typical vertical installation, the submersible motor is located at the lower end of the unit, the water inlet is positioned between the motor and the pump stages, and the discharge outlet is located at the top. Water passes through a series of rotating impellers and stationary diffusers, with each stage progressively increasing the pressure.
Submersible well pumps are widely used for agricultural irrigation, municipal and industrial water supply, groundwater extraction, mine water supply, and other applications that require water to be lifted from deep wells.
How does a submersible well pump work?
A submersible well pump works by using an underwater electric motor to rotate one or more impellers. Water enters through the inlet screen, is accelerated by each impeller, and then passes through a diffuser that converts part of the water velocity into pressure. In a multistage pump, this process is repeated through successive stages until the water has enough pressure to travel through the check valve and discharge pipe to the surface.
Detailed Component and Material List
The following table shows the principal components and available material options for the illustrated SLAPK submersible well pump. The actual configuration depends on pump size, required duty point, water quality, installation depth, and project specifications.
| NO. | Name | Material |
| 1 | Base | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 2 | Regulating Diaphragm | Rubber |
| 3 | Thrust Bearing | M201B* |
| 4 | Thrust Plate | 3Cr13 |
| 5 | Lower Guide Bearing Bracket | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 6 | Motor Casing | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 7 | Rotor Shaft | 45#Steel, 3Cr13 |
| 8 | Upper Guide Bearing Bracket | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 9 | Radial Shaft Oil Seal | Rubber* |
| 10 | Sand Slinger | Engineering Plastics |
| 11 | Connection Segment | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 12 | Key | Steel |
| 13 | Coupling | 35#Steel, SS304/316 |
| 14 | Inlet Section | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 15 | Impeller Shaft | 35# Hard chrome plated, 3Cr13 |
| 16 | Impeller | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 17 | Conical Locking Sleeve | 45#Steel, 3Cr13,SS304/316 |
| 18 | Pump Bowl | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 19 | Shaft Bearing | Rubber*, Bronze* |
| 20 | Sealing Ring | Cast iron, SS304/316L* |
| 21 | Diversion Shell | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 22 | Bumper | Rubber* |
| 23 | Check Valve | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
| 24 | Non-return Valve Body | Cast iron, 304/316/316L/2205/2507/904L SS, Bronze |
Remarks:
1. Components marked with an asterisk (*) are wear parts.
2. Pump materials can be customized according to the application, water quality, and project requirements.
3. The final component and material configuration is subject to the confirmed technical specification.
Figure 1. Main components and water-flow path of a typical multistage submersible well pump. The exact component arrangement may vary according to pump size, motor design, number of stages, and application requirements.
Main Structure of a Submersible Well Pump
A typical submersible well pump consists of several key components that work together to ensure reliable underwater operation.
Key Components and Their Functions
| Component | Main function | Why it matters |
|---|
| Pump stages | Contain the impellers and diffusers | Determine the pump’s flow and head performance |
| Impeller | Transfers rotational energy to the water | Generates water velocity and hydraulic energy |
| Diffuser | Guides the water and converts velocity into pressure | Improves pressure recovery between stages |
| Pump shaft and coupling | Transmit motor torque to the impellers | Maintain stable rotation of the hydraulic components |
| Inlet screen | Allows water to enter while blocking large debris | Helps protect the hydraulic components |
| Submersible motor | Provides underwater driving power | Determines available power and operating reliability |
| Radial and thrust bearings | Support the rotating assembly and axial load | Reduce vibration and maintain shaft alignment |
| Seal and sand-protection components | Limit the entry of water, sand and contaminants into sensitive motor areas | Protect the motor and extend service life |
| Check valve | Prevents reverse flow when the pump stops | Reduces water hammer and helps maintain system pressure |
| Submersible cable | Supplies electrical power to the motor | Must match the voltage, current, installation depth and water conditions |
1. Pump Body and Hydraulic Stages
The pump body is the hydraulic section responsible for moving water and generating the required head. In a multistage submersible well pump, it normally contains:
- Impellers: Rotating components that transfer energy from the pump shaft to the water.
- Diffusers: Stationary components that guide the water from one stage to the next and convert part of its velocity into pressure.
- Pump shaft: The rotating shaft that transmits motor torque to the impellers.
- Pump bowls or stage casings: Structural components that contain and align the impellers and diffusers.
The number of hydraulic stages mainly depends on the required head. Wetted components may be manufactured from cast iron, stainless steel, duplex stainless steel, bronze, or other materials selected according to the water quality and operating conditions.
2. Submersible Motor
The submersible motor is installed below the pump section and provides the power required to rotate the pump shaft and impellers. It is designed for continuous underwater operation when used within the specified operating conditions.
Depending on the motor design, clean water or another approved internal medium may be used for cooling, lubrication, or pressure compensation. The motor housing, winding system, cable connection, bearings, and sealing components must all be suitable for the installation depth, voltage, frequency, water temperature, and expected operating load.
Because motor cooling depends on the surrounding water flow and installation conditions, the pump should not be operated dry or outside the manufacturer’s specified minimum cooling requirements.
3. Pump Shaft and Coupling
The pump shaft and coupling transmit rotational torque from the submersible motor to the impellers. Correct shaft alignment is important because misalignment, worn bearings, or an unbalanced rotating assembly can increase vibration and accelerate wear.
Shaft materials are selected according to the required strength, corrosion resistance, pump size, and water quality. Stainless steel or other corrosion-resistant materials may be used for demanding applications.
4. Motor Sealing and Sand Protection
The sealing arrangement protects sensitive motor components and limits the entry of sand or external contaminants. Depending on the motor design, the protection system may include a radial shaft seal, sand slinger, sealing rings, cable-entry seals, and pressure-compensation components.
The exact arrangement is not identical for every submersible motor. Seal materials and structural details should therefore be selected according to the installation depth, water quality, sand content, temperature, and operating conditions.
5. Inlet Screen
In a typical submersible well pump assembly, the water inlet is located between the motor and the hydraulic pump stages. The inlet screen allows groundwater to enter the pump while reducing the entry of large debris that could damage or block the hydraulic components.
The inlet screen is not designed to make a clean-water well pump suitable for heavy sand, gravel, sludge, or large solids. Water containing significant abrasive particles requires a pump and material configuration specifically selected for those conditions.
6. Check Valve
A check valve may be integrated into the upper discharge section of the pump or installed separately in the discharge line. Its purpose is to prevent water from flowing backward when the pump stops.
By limiting reverse flow, the check valve helps maintain system pressure and reduces reverse rotation and hydraulic shock. The valve arrangement should still be designed according to the complete system, especially for long pipelines, high-head installations, and applications with frequent starts and stops.
Working Principle of a Submersible Well Pump
A submersible well pump uses a submerged electric motor and one or more centrifugal pump stages to convert electrical energy into water flow and pressure.
Step 1: The Motor Starts
When power is supplied through the control system and submersible cable, the motor begins to rotate. The motor shaft transfers torque through the coupling to the pump shaft and impellers.
Step 2: Water Enters Through the Inlet Screen
Groundwater enters through the inlet screen positioned between the motor and the hydraulic pump section. The surrounding water also contributes to motor cooling when the installation provides the required flow past the motor.
Step 3: The Impeller Accelerates the Water
Water enters near the centre of the rotating impeller. The impeller transfers mechanical energy to the water and moves it outward toward the edge of the impeller, increasing its velocity and hydraulic energy.
Step 4: The Diffuser Converts Velocity into Pressure
After leaving the impeller, the water enters a stationary diffuser. The diffuser guides the flow into the next stage and converts part of the water velocity into pressure.
Step 5: Successive Stages Increase the Head
In a multistage submersible well pump, the impeller-and-diffuser process is repeated through several stages. Each stage adds pressure, allowing the pump to overcome the vertical lift, required outlet pressure, and friction losses in the pipeline.
Adding more stages generally increases the available head, but the actual operating flow and head must always be checked on the pump performance curve.
Step 6: Pressurized Water Is Discharged
After passing through the final stage, the pressurized water flows through the check valve and into the discharge pipe. It then travels upward to the storage tank, irrigation network, municipal system, industrial process, or other point of use.
Water-flow path:
Well water → Inlet screen → Impeller → Diffuser → Successive pump stages → Check valve → Discharge pipe → Surface system
How Pump Components Affect Performance and Reliability
| Component | If the component is damaged or unsuitable | Possible operating symptom |
|---|
| Impeller or diffuser | Wear, corrosion or blockage changes the hydraulic passages | Reduced flow, reduced head or lower efficiency |
| Pump shaft or coupling | Wear or misalignment affects rotation | Vibration, noise or uneven operation |
| Inlet screen | Debris restricts the inlet area | Reduced flow and unstable performance |
| Radial or thrust bearing | Wear increases shaft movement | Vibration, abnormal noise or motor overload |
| Seal or sand-protection component | Contaminants enter sensitive areas | Bearing wear, leakage or motor damage |
| Submersible motor | Incorrect voltage, overload or inadequate cooling | High current, overheating or repeated shutdown |
| Check valve | Valve does not close correctly | Reverse flow, loss of pressure or hydraulic shock |
A reduction in flow or pressure does not automatically mean that the pump itself is damaged. Changes in dynamic water level, pipe friction, valve position, voltage, well yield, and system demand can produce similar symptoms. The complete installation should therefore be checked before replacing individual pump components.
Advantages of Submersible Well Pumps
Submersible well pumps offer several practical advantages for groundwater extraction:
- No surface priming: The hydraulic section remains submerged during normal operation.
- Efficient water lifting: The pump pushes water through the discharge pipe rather than relying on surface suction.
- Compact installation: The motor and pump operate as one submerged unit inside the well.
- Low surface noise: Most of the rotating equipment operates underwater.
- Multistage head capability: Multiple pump stages can generate the pressure required for deep-well applications.
- Broad material options: Cast iron, stainless steel, duplex stainless steel and bronze configurations can be selected for different water conditions.
These advantages depend on correct pump selection and installation. Incorrect flow, head, motor power, installation depth, water quality, or cooling conditions can reduce efficiency and service life.
What Information Is Needed to Select a Submersible Well Pump?
Understanding the pump structure explains how the equipment works, but the pump model should be selected according to the actual project duty point and installation conditions.
The required flow should be calculated from the project’s water demand, operating hours, peak demand, storage capacity, and sustainable well yield. The required head should be based on the dynamic water level, elevation difference, required outlet pressure, and pipeline friction loss.
Before selecting a model, prepare the following information:
- Required flow rate
- Static and dynamic water levels
- Well depth and casing diameter
- Discharge-pipe length and diameter
- Required outlet pressure
- Water temperature, sand content and chemical composition
- Available voltage, phase and frequency
- Daily operating hours and starting frequency
The required duty point should then be checked on the pump performance curve. The selected model should operate within the manufacturer’s recommended range rather than being chosen only from its maximum flow, maximum head, or motor power.
For a complete pump selection, first calculate the required flow rate and Total Dynamic Head. Then check the duty point by learning how to read a submersible well pump performance curve. You can also follow our complete guide on how to choose the right submersible well pump for your project.
FAQ
What are the main parts of a submersible well pump?
The main parts include the submersible motor, pump shaft and coupling, inlet screen, impellers, diffusers, pump bowls, bearings, sealing and sand-protection components, check valve, discharge connection, and submersible power cable.
Where does water enter a submersible well pump?
In a typical vertical deep-well pump assembly, water enters through the inlet screen located between the submersible motor and the hydraulic pump stages. The exact arrangement may vary according to the pump and motor design.
Why does a deep-well pump use multiple impellers?
Each impeller-and-diffuser stage adds pressure to the water. Multiple stages allow the pump to generate enough head to overcome the dynamic water level, elevation, outlet pressure, and pipeline friction losses.
Can a submersible well pump run without water?
A standard submersible well pump should not be operated dry unless it is specifically designed and approved for that condition. Insufficient submergence or motor cooling can cause overheating, bearing damage, seal damage, or motor failure.
Conclusion
A submersible well pump combines a submerged electric motor with a multistage centrifugal hydraulic section. The motor rotates the impellers, the diffusers convert water velocity into pressure, and successive stages generate the head required to deliver groundwater to the surface.
Understanding the position and function of the motor, inlet screen, impellers, diffusers, shaft, bearings, seals, and check valve makes it easier to evaluate pump construction, diagnose operating problems, and compare different pump designs.
For pump selection, send SLAPK your required flow, Total Dynamic Head, well diameter, static and dynamic water levels, water quality, voltage, frequency, and operating schedule. Our engineering team can recommend a suitable submersible well pump and provide the corresponding performance curve and technical data.
