What is a Submersible Pump and How Does it Work?

What is a Submersible Pump and How Does it Work?

Submersible pumps are one of the most widely used pump types in construction, municipal, and industrial applications. They show up in lift stations, dewatering operations, sewage systems, and water supply wells across the country every day. Understanding how they work and when to use them helps contractors and facilities managers make better equipment decisions.

Here is everything you need to know about submersible pumps.

What is a Submersible Pump?

A submersible pump is a pump designed to operate fully submerged in the fluid being pumped. Unlike surface mounted pumps that sit above the water and draw fluid up through a suction line, a submersible pump is lowered directly into the fluid and pushes it upward through a discharge pipe.

The motor and pump assembly are sealed in a watertight housing that protects all electrical and mechanical components from the surrounding fluid. This sealed design allows the pump to operate submerged indefinitely without damage.

How Does a Submersible Pump Work?

The operation of a submersible pump follows a straightforward sequence:

Step 1 — Pump is submerged The pump assembly is lowered into the fluid — a wet well, sump, excavation, or other collection point — and positioned at the appropriate depth.

Step 2 — Motor drives the impeller An electric motor sealed within the pump housing drives the impeller to rotate at high speed. The motor is cooled by the surrounding fluid rather than by air cooling as in surface mounted pumps.

Step 3 — Impeller creates flow The rotating impeller draws fluid in through the pump intake at the bottom of the unit and accelerates it outward through centrifugal force.

Step 4 — Fluid is discharged upward The pressurized fluid exits through the discharge port and travels upward through the discharge pipe or hose to the surface.

Step 5 — Automatic operation Most submersible pumps include float switches or level sensors that automatically start the pump when fluid reaches a set level and stop it when the level drops — allowing continuous unattended operation.

Key Advantages of Submersible Pumps

No priming required — because the pump is already submerged in the fluid it does not need to be primed before starting. This eliminates one of the most common operational challenges with surface mounted pumps.

Self cooling — the surrounding fluid cools the motor continuously during operation. Submersible pumps can run for extended periods without overheating concerns that affect air cooled surface pumps.

Quiet operation — submerged operation significantly reduces noise compared to surface mounted pumps. Important for noise sensitive environments like residential areas, hospitals, and schools.

Efficient pumping — pushing fluid from below is more efficient than pulling it from above. Submersible pumps avoid the suction lift limitations that restrict surface pump performance.

Unattended operation — float switch automation allows submersible pumps to operate continuously without constant monitoring. Essential for lift stations, dewatering operations, and other applications requiring 24 hour pumping.

Space efficient — submersible pumps install within the sump or wet well rather than requiring surface space for pump equipment. Valuable in confined installations.

Types of Submersible Pumps

Submersible dewatering pumps — designed for construction site dewatering, sump pumping, and groundwater removal. Handles water with light to moderate sediment content. The most common type on construction sites.

Submersible sewage pumps — engineered specifically for raw sewage with solids. Heavy duty construction, vortex or semi-open impellers for solids passage, continuous duty rating. Used in lift stations, bypass pumping, and municipal wastewater applications.

Submersible slurry pumps — for high solids content applications like mining dewatering and industrial slurry transfer. Hardened wear resistant components for extended service in abrasive conditions.

Submersible well pumps — long narrow profile designed for installation in water supply wells. Used for groundwater extraction and water supply applications.

Submersible effluent pumps — for lightly contaminated water with small solids. Less robust than sewage pumps but more capable than clean water pumps. Used for septic system effluent and similar applications.

Key Specifications to Understand

Flow rate (GPM) — how much fluid the pump moves per minute at operating conditions. Always check the pump curve at your actual operating head — not just maximum GPM at zero head.

Total dynamic head — the total resistance the pump must overcome including elevation change and friction losses. Select based on performance at your operating head.

Solids handling — the maximum solid size the pump can pass without clogging. Match to your actual fluid conditions. Sewage applications need minimum 2 inch solids passage.

Motor horsepower — determines the pump's ability to handle demanding conditions. Must be matched to the application requirements.

Voltage and phase — single phase for smaller residential and light commercial applications. Three phase for commercial and municipal applications. Must match available power supply.

Cable length — the power cable must reach from the pump at operating depth to the power connection at the surface. Confirm adequate cable length for your installation depth.

Duty rating — continuous duty for permanent installations and extended dewatering operations. Intermittent duty for occasional use applications.

Submersible Pump Applications

Construction dewatering — the most common construction application. Submersible pumps lowered into excavation sumps remove groundwater continuously during foundation, basement, and utility trench work.

Lift station operation — every municipal wastewater lift station uses submersible sewage pumps to move wastewater uphill when gravity flow is not possible. Typically installed in pairs for redundancy.

Bypass pumping — submersible sewage pumps provide temporary bypass capacity during sewer main maintenance, rehabilitation, and emergency repair operations.

Wet well pumping — industrial and commercial facilities use submersible pumps to remove wastewater and process water from below grade collection points.

Flood response — portable submersible pumps deployed rapidly to remove standing water from flooded buildings, excavations, and work areas.

Mining and quarry dewatering — submersible slurry pumps handle the abrasive high solids water in mining and quarry pit dewatering applications.

Selecting the Right Submersible Pump

To select the right submersible pump for your application confirm:

• Required flow rate at peak conditions
• Total dynamic head at operating conditions
• Maximum solids size in the fluid
• Available power supply — voltage, phase, and amperage
• Physical constraints — sump dimensions and submersion depth
• Duty requirements — continuous or intermittent
• Fluid characteristics — clean water, dirty water, sewage, or slurry

How Flowcor Equipment Can Help

Flowcor Equipment supplies submersible pumps for dewatering, sewage, and slurry applications to contractors, municipalities, and industrial facilities across the U.S. Tell us your application, flow rate, head pressure, and fluid characteristics and we will recommend the right pump and get you a quote within 1 business hour.

Submit a quote request at flowcorequipment.com or call us at 610-241-6770.