Proper installation of a submersible well pump is essential to extending its service life. Even if the pump has been selected correctly, premature failure can still occur if it is suspended improperly, connected with undersized cables, operated with insufficient submergence, or started before the well and piping system have been properly inspected.
The exact installation procedure depends on the pump size, well construction, discharge piping, motor type, and control system. Large industrial deep-well pumps may also require lifting equipment and site procedures that differ significantly from those used for smaller residential pumps.
This article focuses on the key engineering principles that must be checked before lowering a submersible well pump into the well and carrying out commissioning.
Check the Pump Selection Before Installation
Installation should not begin until the pump duty point has been confirmed.
The selected pump should provide the required flow at the calculated Total Dynamic Head while operating within an acceptable part of its performance curve.
Before installation, confirm the main design data:
- Required flow rate
- Total Dynamic Head
- Pump model and number of stages
- Motor power
- Well casing diameter
- Static and dynamic water levels
- Pump installation depth
- Discharge pipe diameter
- Voltage and frequency
If the hydraulic requirement has not yet been established, start with how to calculate the required submersible well pump flow rate and how to calculate Total Dynamic Head.
A pump should not be installed simply because its maximum head exceeds the depth of the well.
Inspect the Pump and Motor Before Lowering Them into the Well
Check the equipment for transportation damage before installation. The pump shaft or coupling should rotate as specified by the manufacturer, and the cable, connectors and motor leads should not show visible damage.
For a pump and motor supplied separately, verify that the motor and hydraulic section are compatible and correctly coupled. Fasteners should be tightened according to the manufacturer’s requirements.
For water-filled or oil-filled motors, follow the motor manufacturer’s instructions regarding filling, storage and pre-installation checks. These requirements can differ significantly between motor designs.
The nameplate should also be checked against the project electrical supply, particularly voltage, frequency, phase and motor power.
Determine the Correct Pump Installation Depth
The pump should normally be installed below the lowest expected dynamic water level, with sufficient submergence for reliable operation and motor cooling.
At the same time, it should not simply be lowered to the bottom of the well.
For example, suppose a well has:
Total depth: 150 m
Static water level: 35 m
Dynamic water level: 70 m
Proposed pump depth: 100 m
The pump would have approximately 30 m of submergence below the measured dynamic water level.
Whether this is appropriate depends on the motor requirements, seasonal water-level changes and well construction.
The difference between static and pumping water levels is explained in Static Water Level vs. Dynamic Water Level.
Do Not Install the Pump Too Close to the Bottom
The bottom of a well may contain accumulated sand,/static-water-level-vs-dynamic-water-level/ drilling residue or other sediment.
Installing the pump intake too close to this material can increase the amount of abrasive particles entering the hydraulic section. Over time, this may accelerate wear of impellers, diffusers and bearings.
This is especially important in wells that already produce sand.
The installation depth should therefore balance two requirements: keeping the pump safely submerged while maintaining an appropriate distance from the bottom and other problematic areas of the well.
For wells with significant sediment, see our guide on selecting a submersible well pump for sandy water.
Check the Well Diameter and Pump Clearance
Before lowering the pump, confirm the actual internal diameter of the well casing.
The pump must have sufficient clearance to pass through the casing, joints and any changes in internal diameter. A nominal “8-inch well” should not automatically be assumed to have enough clearance for every pump described as an 8-inch model.
Check the manufacturer’s actual maximum pump outside diameter.
Adequate clearance also makes installation and future removal easier.
For large industrial pumps, the straightness of the well can become important because casing deviation may prevent a long pump assembly from reaching the intended installation depth.
Motor Cooling Must Be Considered
Submersible motors depend on the surrounding water for cooling.
In a normal borehole installation, water moving toward the pump intake often passes along the motor surface and removes heat. However, the actual cooling condition depends on the well geometry, water entry points, pump position and motor design.
If water enters the well above the pump, or if the pump is installed in a large-diameter casing, tank or open reservoir, sufficient water velocity around the motor may not occur naturally.
In these situations, a cooling sleeve or flow inducer sleeve may be required.
Motor cooling requirements should be checked against the motor manufacturer’s specified minimum cooling velocity.
Select the Correct Rising Main
The discharge or rising pipe carries water from the pump to the surface.
Its diameter should be selected for the required flow rather than simply matching the pump outlet connection.
An undersized pipe increases water velocity and friction loss. This raises Total Dynamic Head and increases the energy required from the pump.
An excessively large pipe may reduce friction but increase installation cost and physical weight.
Pipe pressure rating is also important. The lower sections of a deep-well rising main may experience substantial pressure, particularly during starting, stopping or abnormal operating conditions.
The pipe, couplings and fittings should therefore be rated for the expected system pressure.
Check Valve Location Matters
A check valve prevents reverse flow when the pump stops.
Depending on the pump and installation, a check valve may already be incorporated into the pump. Deep installations may require additional valves in the rising main according to the pump manufacturer’s recommendations and system design.
Check valves should not simply be added at arbitrary intervals. Incorrect valve selection or placement can contribute to hydraulic shock and other operating problems.
For high-head systems, water hammer should be evaluated as part of the pipeline design rather than treating the check valve as an isolated component.
Support the Pump Correctly
The pump must be supported by the rising main or by the installation method specified for the system.
The electrical cable is not a lifting cable.
Never lower or suspend a submersible well pump by its power cable. Doing so can damage the cable connection, insulation or motor lead and may cause electrical failure after installation.
For heavy pumps, use suitable lifting equipment and follow the manufacturer’s approved lifting points and procedures.
The combined weight of the pump, motor, rising pipe, cable and water column can become substantial in deep industrial wells.
Protect the Submersible Cable
The power cable runs alongside the rising pipe and must be protected throughout the installation.
It should be secured at appropriate intervals so that it cannot move freely, rub against the casing or become trapped between pipe joints.
Cable guards or suitable fastening methods may be required depending on the installation.
The cable should not be pulled excessively tight. A small allowance should remain for movement and installation tolerances.
Before lowering the pump, inspect the entire cable for cuts, crushed sections or insulation damage.
Select the Correct Cable Size
Cable size depends on more than motor horsepower.
The electrical design should consider:
- Motor current
- Supply voltage
- Cable length
- Starting current
- Allowable voltage drop
- Installation conditions
Long deep-well cables can create significant voltage drop if the conductor is too small.
Low voltage at the motor terminals may lead to poor starting performance, increased current and motor overheating.
For this reason, the pump supplier or electrical engineer should calculate cable size using the motor data and total cable length rather than choosing cable by visual size or previous experience alone.
Make Cable Connections Watertight
Any submerged cable joint must be designed for continuous underwater service.
Poor cable splicing is a common source of deep-well pump problems because moisture entering the connection can eventually cause insulation failure.
Use a connection method approved for the motor and cable system, and perform the required insulation tests before lowering the pump.
Repairing a bad cable connection after installation may require removing the entire pump assembly from the well, so this is not an area where installation quality should be compromised.
Install the Pump Carefully
During lowering, the pump should move freely through the casing.
Do not force the assembly if it becomes stuck. Determine whether the obstruction is caused by a casing joint, well deviation, pipe coupling, cable position or insufficient clearance.
The cable should be monitored continuously so it does not become pinched between the rising pipe and casing.
For long installations, pipe sections are normally connected progressively as the pump is lowered.
Large pumps should be installed using suitable lifting and handling equipment with personnel experienced in deep-well installations.
Electrical Protection Should Be Ready Before Startup
A submersible motor should not be connected directly without appropriate electrical protection.
Depending on the system, protection may include:
- Overload protection
- Short-circuit protection
- Phase-loss protection
- Phase-imbalance protection
- Under-voltage and over-voltage protection
- Dry-running protection
- Water-level protection
Larger motors may also use star-delta starters, soft starters or variable frequency drives depending on the electrical system and application.
Protection settings should be based on the actual motor specifications.
Check Rotation Before Normal Operation
For three-phase pumps, correct rotation is essential.
Incorrect phase sequence can cause the pump to rotate in the wrong direction, resulting in substantially reduced flow and head and potentially undesirable operating conditions.
Rotation should be checked according to the manufacturer’s commissioning procedure.
Do not allow the pump to operate for an extended period under incorrect rotation simply to determine whether performance improves.
Start the Pump Against Controlled System Conditions
When commissioning a new well pump, avoid immediately operating the system at an uncontrolled maximum flow.
Start according to the manufacturer’s procedure and monitor the discharge while the well stabilizes.
During initial operation, record:
Flow rate
Discharge pressure
Dynamic water level
Motor current
Voltage
These measurements establish the actual operating point.
Compare them with the selected duty point and submersible well pump performance curve.
Monitor the Dynamic Water Level During Startup
A well may appear to have sufficient water before pumping but experience significant drawdown once the pump starts.
Monitor the dynamic water level during commissioning, especially if the well yield is uncertain.
If the water level continues to fall toward the pump intake, reduce the flow or stop the pump and investigate the well capacity.
Installing a larger motor does not solve insufficient well yield.
The pump flow must remain compatible with the sustainable output of the well.
Check Motor Current
Motor current provides useful information about pump operation.
During commissioning, measure the current on each phase and compare it with the motor nameplate and manufacturer’s operating limits.
Abnormal current can indicate problems such as incorrect voltage, phase imbalance, incorrect rotation, unsuitable operating conditions or mechanical issues.
Record the initial current values. They can later serve as useful baseline data when troubleshooting pump performance.
Record Commissioning Data
A good installation should finish with documented commissioning data rather than simply confirming that water reaches the surface.
Record at least:
- Pump model
- Motor model and power
- Installation depth
- Static water level
- Dynamic water level
- Flow rate
- Discharge pressure
- Voltage
- Current on each phase
- Control settings
These values provide a reference for future maintenance.
If flow or pressure decreases several years later, comparing new measurements with the original commissioning data can help determine whether the problem comes from the pump, well or pipeline.
Common Submersible Well Pump Installation Mistakes
Many premature failures can be traced to installation rather than pump manufacturing.
Common mistakes include installing the pump without confirming the dynamic water level, placing it too close to bottom sediment, using an undersized cable, suspending the pump by its electrical cable, ignoring motor cooling requirements, and operating without dry-run or overload protection.
Another common mistake is changing the pump model during installation without recalculating the hydraulic duty. A larger pump may appear to provide more safety but can move the operating point away from the intended range or exceed the well yield.
Correct installation begins with correct pump selection. Our complete submersible well pump selection guide covers the hydraulic and application data that should be established before installation.
Before You Install: Final Checklist
Before lowering the pump into the well, confirm:
- Pump model matches the required flow and TDH.
- Motor voltage and frequency match the power supply.
- Pump diameter fits the actual casing.
- Installation depth provides adequate submergence.
- Pump is not positioned too close to sediment.
- Motor cooling conditions are acceptable.
- Rising pipe diameter and pressure rating are suitable.
- Cable size is correct for motor current and length.
- Cable joints are waterproof and tested.
- Electrical protection is installed and correctly set.
- Suitable lifting equipment is available.
- Commissioning instruments are ready.
For industrial, municipal, mining and large irrigation installations, the final installation procedure should also follow the pump and motor manufacturer’s project-specific instructions.
Selecting a Pump Before Installation
Installation quality cannot correct an incorrectly selected pump.
Before ordering, confirm the required flow, TDH, dynamic water level, well diameter, installation depth, water quality, voltage and daily operating conditions.
SLAPK can use these project parameters to recommend a suitable model from our submersible well pump range, including the performance curve, motor specification and installation-related technical data.
This allows the pump, motor, cable and installation conditions to be evaluated as one complete system rather than as separate components.
