Submersible deep well pumps are widely used in groundwater extraction, agricultural irrigation, and municipal water supply systems. Although these pumps are designed for long-term underwater operation, electrical issues, improper installation, and mechanical wear can still lead to failures.
Based on field service experience, below are six of the most common problems — along with their causes and practical troubleshooting methods.
①No Water, Intermittent Flow, or Low Discharge
This is one of the most frequently reported issues in deep well pump applications.
Possible Causes
- The motor fails to start due to low voltage or undersized cable, resulting in insufficient torque
- Pipeline or pump inlet is blocked by debris or sediment
- Leakage in the discharge pipeline reduces effective flow
- Water level in the well drops below the pump intake
- Pump rotates in the wrong direction (three-phase systems)
- Impeller or seal ring is severely worn
- Impeller is mechanically stuck
- Shaft or coupling is damaged
Troubleshooting Methods
- Check the power supply and wiring; ensure voltage meets requirements
- Clean the pipeline and pump inlet screen
- Inspect all pipe connections and repair leakage points
- Measure dynamic water level and lower the pump if necessary
- Verify motor rotation direction and correct phase sequence
- Replace worn impeller or seal ring
- Disassemble pump and remove debris
- Repair or replace damaged shaft components
②Excessive Current or Ammeter Fluctuation
Abnormal current usually indicates overload or internal mechanical resistance.
Possible Causes
- Pump operating beyond rated flow or head range
- Bearing damage (graphite bearing, rubber bearing, or shaft sleeve wear)
- Thrust bearing failure causing impeller downward movement
- Pump shaft bending or misalignment
Troubleshooting Methods
- Adjust discharge valve to bring pump back to rated operating point
- Measure operating current and compare with nameplate value
- Replace worn bearings and check bearing clearance
- Replace thrust bearing and thrust plate if damaged
- Inspect shaft straightness and alignment; repair if necessary
③Motor Winding Insulation Resistance Below 0.5 MΩ
Low insulation resistance is a serious warning sign that may lead to motor failure.
Possible Causes
- Insulation aging or mechanical damage
- Water ingress through damaged cable
- Mechanical seal failure allowing moisture into motor
Troubleshooting Methods
- Use a megohmmeter to test insulation resistance
- If windings are damp, dry the motor before operation
- Repair or replace damaged cables
- Inspect and replace faulty mechanical seals
- Rewind the motor if insulation deterioration is severe
④Pump Cannot Start and Produces a Humming Sound
A humming motor usually means the motor is energized but unable to rotate.
Possible Causes
- Phase loss or open circuit causing single-phase operation
- Bearing seizure or excessive friction
- Impeller jammed by foreign objects
- Supply voltage too low
Troubleshooting Methods
- Check power supply phases and control circuit
- Inspect and repair or replace seized bearings
- Disassemble pump and remove blockage
- Measure and stabilize supply voltage
⑤Severe Vibration During Operation
Excessive vibration can quickly damage bearings, seals, and the motor.
Possible Causes
- Rotor imbalance
- Impeller imbalance
- Bent shaft
- Bearing wear
- Loose coupling or foundation bolts
- Misalignment between pump and motor
- Thrust bearing wear
- Pump partially buried in sediment
Troubleshooting Methods
- Perform dynamic balancing of rotor and impeller
- Check shaft runout and straighten or replace if bent
- Replace worn bearings or shaft sleeves
- Tighten all mechanical connections
- Re-align pump and motor shafts
- Inspect installation depth and remove surrounding sediment if necessary
⑥Motor Winding Burnout
Motor burnout is usually the result of long-term electrical or cooling problems.
Possible Causes
- Motor not fully filled with clean water (insufficient cooling)
- Single-phase running condition
- Long-term overload operation
- Frequent starting and stopping
Troubleshooting Methods
- Ensure the motor is properly filled with clean water before operation
- Install and verify motor protection devices
- Monitor operating current regularly
- Use valve control to keep pump within rated load range
- Avoid frequent start-stop cycles
Final Recommendation
Regular inspection, proper pump selection, and stable electrical supply are essential to ensure reliable long-term operation of submersible deep well pumps.
Preventive maintenance always costs less than emergency repairs.