Introduction
If you’re new to water systems, and you need a pump to lift water underground, you’ve probably heard of a submersible pump — but what exactly is it?
Submersible pump is a kind of pump designed to work completely underwater, pushing water up to the ground.
Learning the basic parts of a submersible pump is important for you to choose a suitable pump for their needs. And during the server time of your pump, it can help solve small problems on your own, and compare different pumps so you get the best choice for your own needs.
In this guide, we’ll introduce all the essential parts of a submersible pump in a clear and simple way — no technical background needed.
Main Parts of a Submersible Pump
Pump Casing (Outer Body)
The pump casing is the outer shell that protects all the internal parts and keeps the whole pump stable during operation.
Different types of materials can be selected based on different using environments. It’s usually made from stainless steel, aluminum, cast iron, or strong engineering plastics. If it’s used in clean water, cast iron and aluminum are your best choices. If it’s used in dirty water or seawater, stainless steel and engineering plastic are needed to provide a longer sever life.
A good choice of pump casing is important because it can protect the inner part of the pump from different kind of water, and directly affect how long the pump will last and how well it can work in different water environments.
Intake Screen / Strainer
The intake screen, also called a strainer, is located at the bottom of the pump. Its job is simple but important. It prevents sand, stones, and other impurities from getting into the pump. By keeping impurities out, the intake screen helps protect the internal parts.
Impeller
The impeller is a part that moves water through the pump and creates the pressure needed to push it upward. There are three common types: open impellers have no side walls and are easier to maintain; semi-open designs have a partial cover and can give a good performance; closed impellers are fully enclosed and provide higher efficiency.
Impellers can be made from stainless steel, brass, or engineering plastics. The material is important because it will affect how well the pump handles corrosion, sand, or abrasive particles. For example, stainless steel can give strength and long service life in harsh or sandy water, while engineered plastics can be more cost-effective and still work well in clean water systems.
The impeller design and material have a noticeable impact on performance. A well-designed impeller can improve the flow, and make the pump work smoothly. It also affects how much noise or vibration the pump produces and how well it handles debris. In short, the impeller is one of the main factors that determines how efficient, durable, and suitable a submersible pump is for a specific application.
Diffuser / Bowl
The diffuser (bowl) is the part of the pump that leads water smoothly from one impeller stage to the next. The shape of the diffuser is essential for efficient pumping to help convert the high-speed water coming off the impeller into higher pressure.
Diffusers play a key role in building pressure. While the impeller creates water movement, the diffuser helps turn that movement into usable pressure, making the pump work more stably.
In deep well pumps, multi-stage diffusers are especially important. Each diffuser-and-impeller pair adds another “boost” of pressure, making the pump to lift water from much greater depths. The more stages a pump has, the higher it can lift water. That is why deep well pumps often rely on several diffusers working together to achieve strong, steady performance.
Pump Shaft & Shaft Sleeve
The pump shaft is the part that connects the impeller to the motor, transferring the motor’s rotational force so the impeller can turn around and move water. Around the shaft, you’ll often find a shaft sleeve, which plays a role in protecting the layer to prevent wear, especially in pumps that handle water with sand, dirty water and seawater.
The correct connection between the shaft and motor is extremely important. If the shaft is not connected properly, it will cause vibration, noise, and uneven wear for internal parts. The incorrect connection may cause reduced efficiency, seal failure, or even motor damage during the lifespan of the pump. When every part is connected correctly, the pump will run smoothly, work longer, and have a good performance.
Mechanical Seal
The mechanical seal is the component that keeps water from leaking into the motor section of the pump. It forms a tight barrier between the wet side of the pump and the electrical parts, making sure the pump works safely and reliably. These seals are made from ceramic, carbon, stainless steel, or silicon carbide; each of them will have different levels of resistance to wear, heat, and corrosive water conditions.
Seal quality plays a major role in the whole lifespan of the pump. A good mechanical seal can cause less friction, prevent leakage of water, and protect the motor from moisture damage. If the seal fails, the motor can short out or corrode, destroying the pump. In short, a reliable mechanical seal keeps the pump safe, efficient, and running longer.
Check Valve (Non-Return Valve)
The check valve, also known as a non-return valve, stops water from flowing backward once the pump shuts off. Without it, water in the pipe could rush back down, causing pressure shocks or forcing the pump to restart under load. This valve helps protect the impellers and the entire plumbing system from stress. In many submersible pumps, the check valve is already built in, making installation easier and making the pump run smoother, more reliably.
Motor Components of a Submersible Pump
Electric Motor
The electric motor is the power source of the pump. It drives the shaft and impeller to lift water. Submersible pumps generally use either oil-filled or water-filled motors.
Oil-filled motors are less costly and well-lubricated, and run quietly. It’s suitable for many household and agricultural applications.
Water-filled motors are cooled directly by the water around them. It’s a good choice for drinking-water systems or environments where oil must be avoided.
Learning the difference helps you choose a pump that fits both the water quality and the working conditions.
Stator and Rotor
The stator and rotor work together inside the motor to create rotation. The stator stays fixed and produces a magnetic field, and can make the rotor spin inside it, turning electrical energy into mechanical energy that drives the shaft and impeller. Proper insulation inside the stator is extremely important because it protects the windings from moisture, heat, and electrical damage. Good insulation helps prevent the motor from burning, reduces power loss, and makes sure the pump can run reliably in underwater conditions for many years.
Bearings (Upper & Lower)
Bearings support the motor shaft and keep it running with minimal friction. Most submersible pumps have both upper and lower bearings to ensure stable work, especially during long operation periods.
There are two common types: water-lubricated bearings, which rely on the water for lubrication and are often used in drinking-water or clean-water systems, and oil-lubricated bearings, which provide more stable operation and better protection in water with sand. The popor bearing type helps the pump run quietly, reduces wear, and maintains long-term reliability.
Thrust Bearing (Deep Well Pumps)
The thrust bearing is designed to handle the force created by multi-stage impellers in deep well pumps. As the pump operates, the impellers lift water upward, creating downward pressure on the shaft, and the thrust bearing takes the pressure to keep everything running smoothly. Because deep well pumps often keep running for a long time, a reliable thrust bearing is important. It can help prevent wear, reduce vibration, and play a key role in ensuring the pump delivers stable performance over many years.
Motor Housing
The motor housing is the sealed, waterproof casing that surrounds the motor and keeps it safe from the water and pressure from deep underground. Its job is to make sure no moisture can enter the motor chamber, even when working for a long time. A strong, well-sealed housing protects the motor from leakage, corrosion, and external pressure, helping the pump work longer.
Electrical and Control Components
Power Cable
The power cable supplies electricity to the motor, and it’s specially designed to be waterproof with thick, reliable insulation to prevent moisture. Submersible pumps commonly use flat cables, which are easy to install and seal at the wellhead, or round cables, which can offer better strength and durability. Cable quality affects safety. A poor-quality cable will cause leaks, short circuits, or voltage drops, all of which can damage the motor or create serious electrical risks.
Control Box (For Deep Well Pumps)
Deep well pumps can come with an external control box instead of having everything built inside the motor. Inside this small control box, you’ll usually find just two key components: a capacitor for starting the motor and an overheat protector for basic safety.
The main reason for having an external control box is maintenance convenience. Since deep well pumps are installed underwater for long periods, replacing a damaged capacitor inside the pump would require pulling the entire unit out of the well — a process that takes time, labor, and cost. With an external control box, the capacitor and protection components are easy to get, making repairs or replacements much simpler and far more economical.
Cable Splice / Waterproof Joint
The cable splice, or waterproof joint, is the section where the motor’s built-in cable connects to the surface cable. Its job is to create a completely watertight seal so no moisture can enter the connection. Common types include heat-shrink joints, which use heat to tighten and seal the tubing around the cables, and resin-sealed joints, where a special resin is poured into a protective mold to create a solid, waterproof bond. A properly sealed joint is essential for safe, long-term operation, as even a small leakage can cause short circuits, voltage drop, or motor damage.
Optional or Application-Specific Parts
Depending on the installation and working environment, some submersible pumps include additional parts can improve performance or make the pump smart.
Like sand guards can reduce wear in sandy wells, cooling jackets that help keep the motor at a safe temperature in low-flow conditions, or float switches for automatic water level control. These parts aren’t standard on every pump, but they’re useful additions that can extend the pump’s life, improve efficiency.
Cutter System (For Sewage Submersible Pumps)
In sewage submersible pumps, the cutter system is an added feature that helps the pump handle solids. This system usually includes a knife plate or a grinder-style impeller designed to cut materials like rags, paper, or other impurities before they enter the pump. By cutting solids into smaller pieces, the cutter system reduces clogging, keeps the pump running normally, and makes sure the pump work reliable operation in wastewater environments.
Float Switch or Level Sensor
A float switch or level sensor provides automatic ON/OFF control based on the water level. When the water rises, the switch turns the pump on, and when the level drops, it shuts the pump off. This simple feature is important for preventing dry running, which can overheat and damage the pump. With a float switch, the pump can work automatically without keeping your eye on it.
How The Parts Work Together
Here’s a simple, beginner-friendly look at how a submersible pump works as one system:
Water first enters the pump through the intake screen, which blocks sand and debris. The impeller then spins and pushes the water upward, while the diffusers help build more pressure with each stage. The shaft connects the impeller to the motor, transferring power smoothly so everything turns as it should. Meanwhile, the motor stays sealed inside its waterproof housing, protected from water and pressure.
Common Materials Used for Submersible Pump Parts
Submersible pumps use different kinds of materials to handle different environment.
Stainless steel is usually used for casings, shafts, and impellers because it resists rust and handles harsh water conditions well.
Cast iron gives great strength, making it common in sewage pumps or heavy-duty components.
Engineering plastics of PPO or POM, are usually used for deep well pump impellers. It’s cost-effective， sand-resistant, and suitable for clean-water applications.
For sealing parts, materials such as EPDM or Viton are used. Both of them provide strong resistance to heat and chemicals, helping the pump stay leak-free.
Conclusion
A submersible pump may look like a single unit, but it’s actually a combination of many important parts working together — from the casing and intake screen to the impeller, diffusers, motor, seals, bearings, and cables. Each part helps keep the pump efficient, protected, and reliable. Choosing a pump built with quality materials and well-designed parts makes a big difference in performance, maintenance needs, and whole lifespan.
If you’re looking for reliable products, we are a professional manufacturer of submersible pumps and pump accessories, ready to help you choose the right solution for your application.
FAQ
What are the most important parts of a submersible pump?
The most important parts include the pump casing, intake screen, impeller, diffusers, shaft and bearings, motor, mechanical seal, and power cable. Each part helps the pump work efficiently and protecting the pump.
Which material is best for impellers?
It depends on the water and application. Stainless steel is durable and corrosion-resistant, ideal for seawater or dirty water, while engineering plastics work well in clean-water systems and are cost-effective.
Do all submersible pumps have a check valve?
Not always. Many submersible pumps include a built-in check valve to prevent backflow, but smaller or shallow-water models will need an external valve instead.
What causes mechanical seal failure?
Mechanical seals can cause failure due to wear, poor alignment, dry running, high temperatures, or abrasive particles in the water. Proper installation and quality materials help prevent failure.
Why do deep well pumps use multiple stages?
Multi-stage designs allow the pump to generate higher pressure, which is needed to lift water from greater depths. Each stage adds an extra “boost,” making deep well pumping efficient and reliable.
