Troubleshooting 101: Common Submersible Pump Problems and Their Solutions
Troubleshooting 101: Common Submersible Pump Problems and Their Solutions
Quietly submerged and out of sight, deep-well pumps are engineering marvels. Learn how to pinpoint, diagnose, and resolve common issues right from the surface.
Submersible pumps are the unsung heroes of modern water systems. Quietly submerged deep within wells, sumps, or utility pits, these systems push water to the surface efficiently and reliably.
Because they operate completely underwater, they are shielded from weather and external wear. However, their greatest advantage—being out of sight and out of mind—is also their greatest challenge when things go wrong. Pulling a pump up from hundreds of feet underground is no small feat, so knowing how to diagnose problems from the surface is invaluable.
Whether you rely on a submersible pump for household water, agricultural irrigation, or wastewater management, this comprehensive guide will help you identify common issues and implement their solutions safely.
The Quick Diagnostics Checklist
Before diving into deep repairs, use this high-level troubleshooting matrix to match your physical symptoms to their potential culprits and fast fixes:
| Symptom | Most Likely Cause | Primary Solution |
|---|---|---|
| Pump won't start | Electrical power loss or failed pressure switch | Reset breaker, test switch contacts |
| Runs, but no water flows | Clogged intake or failed check valve | Clean screen, inspect check valve |
| Rapid cycling (on/off constantly) | Waterlogged pressure tank | Adjust tank pre-charge pressure or replace bladder |
| Pump runs continuously | Drop pipe leak or worn impellers | Check for drop-pipe leaks, inspect pump stages |
| Trips circuit breaker instantly | Short circuit in motor or cable | Test insulation resistance with a megohmmeter |
The Pump Won't Start (No Water, No Sound)
There is nothing more frustrating than turning on a tap and getting absolute silence. When a submersible pump refuses to start, the issue is almost always electrical or control-related.
Common Causes
- • Tripped Breaker or Blown Fuse: A sudden electrical power surge or motor overload has tripped the main electrical protection.
- • Faulty Pressure Switch: The switch contacts are burnt, corroded, or stuck open, failing to signal the pump to turn on.
- • Failed Control Box: For three-wire pumps, the start capacitor, run capacitor, or relay inside the control box has burnt out.
How to Fix It
- Check the Main Panel: Locate the circuit breaker dedicated to your pump. If it is tripped, flip it completely to Off and then back to On. Do not force it if it trips again.
- Inspect the Pressure Switch: Turn off the power and remove the cover. Check for burnt contacts or debris (like dust or ants) wedged between points. Clean contacts gently with very fine sandpaper.
- Test the Control Box: Look for signs of overheating or bulging/leaking capacitors inside the wall-mounted control box. Defective capacitors can easily be swapped.
The Pump Runs, but Delivers No Water
If you can hear your system humming or see the pressure switch engage, but your taps are running completely dry, the pump motor is spinning but failing to lift water to the surface.
Common Causes
- • Clogged Intake Screen: Debris, silt, sand, or iron bacteria have blocked the suction screen at the base of the pump unit.
- • Worn or Damaged Impellers: Sand can erode plastic or brass impellers over time, destroying their hydraulic lifting capacity.
- • Stuck Check Valve: The spring-loaded valve designed to stop backflow is stuck closed.
- • Dropped Water Table: The water level in your well has dropped below the physical depth of the pump's intake.
How to Fix It
- Verify Water Level: If your well has a low yield, turn off the pump for 30 to 60 minutes to let the static water level recover.
- Clean the Intake Screen: If you pull the pump, clear away any biological slime, scale buildup, or packed silt blocking the screen.
- Inspect Check Valve: Ensure the check valve near the discharge outlet moves freely and isn't jammed by mineral scaling.
Rapid Cycling (Turning On and Off Continuously)
"Rapid cycling" is the silent killer of submersible pumps. It occurs when a pump turns on, builds pressure instantly, cuts off, and restarts immediately in a rapid loop. This causes the motor winding to overheat, quickly ruining the unit.
Common Causes
- • Waterlogged Pressure Tank: The internal air bladder has ruptured or lost pre-charge pressure. Without an air cushion, the pressure spikes instantly upon startup, cutting the pump right back off.
- • Misadjusted Pressure Switch: The gap between cut-in and cut-out limits is set too narrow.
How to Fix It
- Perform the "Knock" Test: Tap the pressure tank. The top should sound hollow (air), and the bottom should sound dull and metallic (water). Solid sound top-to-bottom means it's waterlogged.
- Check & Adjust Pre-charge Pressure: Turn off the pump, drain all water. Use a tire pressure gauge on the tank's air valve. It must be exactly 2 psi below your cut-in switch limit (see formula below).
- Replace the Bladder or Tank: If water leaks from the air valve when checked, the internal bladder is torn; the tank must be replaced.
Pre-Charge Calculation
To ensure a proper air-cushion buffer, calculate your target pressure using the formula:
Example: If your pump switches on at 30 psi, the tank's static air pressure should be set to exactly 28 psi.
The Pump Runs Constantly (Won't Shut Off)
A pump that never stops running will lead to soaring electricity bills and will rapidly burn out its motor. Finding the root cause is critical.
Common Causes
- • Leaking Drop Pipe: A physical rupture or hole inside the well's connection pipe allows water to spray back into the well rather than reaching the surface.
- • Worn Pump Stages: Mechanical wear keeps the pump from building enough pressure to reach the cut-out limit on the pressure switch.
- • Faulty Pressure Switch: The switch is stuck physically, or the pressure-sensing tube is clogged with silt.
How to Fix It
- Clean Switch Nipple: Turn off power, detach the tube/pipe connected to your switch, and clear any packed rust or scale.
- Check for Underground Leaks: Look for wet patches on your lawn. Listen closely to the wellhead; if you hear rushing water while the pump runs but no home fixtures are open, you likely have a ruptured pipe in the well casing.
- Adjust Switch Cut-Out: If your older pump cannot reach its 50 psi cut-out, temporarily lower the switch cut-out pressure so it shuts off safely until replaced.
Tripping the Circuit Breaker Repeatedly
If the circuit breaker trips instantly when the pump tries to start up, you are facing a severe, direct electrical ground fault or short circuit.
Common Causes
- • Short in Motor Windings: The motor winding's internal varnish insulation has failed, grounding the electrical current directly to the pump's chassis.
- • Damaged Power Cable: The submersible wire has rubbed raw against the well's metal casing, exposing live wire directly to the water.
- • Locked Rotor: Silt or a stone has jammed the impellers, blocking the shaft from rotating and forcing the motor to draw massive starting current (amps).
How to Fix It
- Perform Electrical Tests: Use a digital multimeter or insulation tester (megger) to check the resistance (Ω) across the motor leads and from each lead to the ground connection. Low resistance to ground signals a short circuit.
- Pull the Pump: If electrical tests confirm a short or grounded wire, you must hoist the pump to repair raw spots on the cable, or replace the entire motor assembly.
Preventative Maintenance: Keeping Your Pump Alive
While troubleshooting is critical when a breakdown occurs, proper prevention remains your best investment. Keep your submersible water system running smoothly with these strategic maintenance protocols:
Install a Dry-Run Protector
If your well has a fluctuating water yield, use a dry-run sensor that immediately powers down the pump if water runs dry, preventing severe heat damage.
Keep the Well Clean
Periodically schedule well chlorination or cleaning to arrest the growth of iron bacteria and mineral scale that otherwise clog up your pump's inlet.
Monitor Amp Draw
Track the running current of your pump once a year. A steady upward creep in amperage signals internal wear and mechanical drag on the bearings or shaft.
When to Call a Professional
While basic electrical diagnostics, pressure switch cleaning, and pressure tank calibrations can be safely managed by an experienced DIYer, pulling a deep pump is dangerous and physically punishing work.
If your troubleshooting reveals a split drop-pipe deep inside the well casing, a damaged electrical wire underwater, or a completely burned-out motor, you should immediately contact a licensed water well contractor.
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The Sando Editorial Team consists of pump technology experts and engineers at Sando Rotary Equipments, dedicated to sharing insights and innovations in the fluid handling industry.
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