When a borehole pump stops, the water stops. On a farm that means stressed crops within days. On a water supply project it means angry users within hours. The good news: most borehole pump problems show clear symptoms, and many causes can be checked in the field before you pull the pump.
This guide matches common symptoms to their possible causes and checks. It is written for our QJ/QJT-type submersible borehole pumps, but most checks apply to any borehole submersible. One rule before the table: all electrical work — measuring voltage, swapping phases, opening panels or terminal boxes — must be done by a qualified electrician or trained technician. Site staff can do the mechanical checks (valve position, water level, listening for flow).
Before You Start
Collect three things before touching anything:
- The pump model from the nameplate (for example 250QJ80-80/4).
- The installation data: well depth, static and dynamic water level, how deep the pump hangs.
- The electrical readings if a qualified person can get them safely: supply voltage and running current.
With these, most diagnosis takes minutes instead of days. Two more safety rules: switch off and lock the power before anyone touches cables or the panel, and never run a water-filled submersible motor dry — the motor cavity must be filled with clean water, and the first impeller must sit at least 3 m below the dynamic water level.
Symptom → Possible Cause → Checks Table
Each row gives possible causes, not verdicts. Work through the checks in order; the simple ones come first.
| Symptom | Possible causes | Field checks | Next step if checks do not solve it |
|---|---|---|---|
| 1. Motor runs, but no water comes out | Water level dropped below the first impeller; discharge valve closed or blocked; leaking or broken rising pipe; wrong rotation after rewiring | Check the dynamic water level (first impeller needs ≥3 m submergence). Check the valve position. Listen for water movement in the pipe. An electrician can swap any two phases to correct rotation. | Have the pump pulled and the impellers inspected for wear or damage. |
| 2. No water, and the motor does not run at all | No supply voltage; a lost phase; control panel protection has tripped; damaged cable or cable joint | An electrician measures voltage at the panel (standard supply: 380 V ±5% three-phase), checks breakers and protection relays, and tests cable insulation and continuity. | If the motor winding or insulation has failed, the unit needs workshop repair or replacement — contact us with the model number. |
| 3. Flow is smaller than before | Falling water table; worn impellers; clogged strainer or non-return valve; scale in pipes; wear from sand | Measure the dynamic level and compare with installation records. Measure flow and motor current; low current together with low flow may point to wear or blockage. | If performance keeps falling after cleaning, send us the model and duty data to discuss spares or a replacement quote. |
| 4. Pump starts and stops too often | Water level too low for the pump’s intake; pump oversized for well yield; faulty level or pressure switch; leaking non-return valve | Compare pump flow with the well’s real yield. Check switch settings. Watch whether water flows back down when the pump stops. | Frequent starting overheats motors. If the pump turns out to be oversized, we can help re-select a smaller duty point. |
| 5. Breaker trips or overload relay operates | Low or high supply voltage; phase loss; sand in the pump; damaged bearings; water in a cable joint | An electrician measures voltage and current on all three phases while running and tests cable insulation resistance. Current far above the nameplate value may point to a mechanical or electrical fault. | Repeated tripping with normal voltage may indicate internal damage — stop the pump to protect the motor and contact us. |
| 6. Water contains sand | Well screen or gravel pack problem; pumping level pulled down too far; pump oversized for the well | Reduce the flow with the discharge valve and see whether sand decreases. Check whether the sand started after the water level dropped. | Sand wears impellers and bearings. Our pumps are rated for water with solids ≤0.01% by mass. If the well keeps producing sand, the well itself needs service first; then we can help assess pump wear. |
| 7. Abnormal noise or vibration | Cavitation from too-low submergence; worn bearings; loose coupling; motor running without its water fill | Check the dynamic level first — noise together with falling flow may indicate cavitation. Confirm the motor was filled with clean water before installation. | Grinding or knocking that continues at the correct level may indicate bearing or mechanical damage — have the unit pulled and inspected. |
General rule for the table above: electrical checks, phase swapping, and opening any panel or motor terminal box are jobs for a qualified electrician or trained technician only.
The Three Most Common Root Causes
Most failures of water-filled submersible borehole pumps can be traced to three root causes:
1. Dry running. These motors are water-filled. Running without water in the motor, or with the water level below the first impeller, can destroy bearings and windings quickly. Keep at least 3 m of submergence above the first impeller, and never test-run the unit out of water. If your well level falls in the dry season, ask us about dry-run protection options in the control panel.
2. Bad power. The standard motor is built for 380 V ±5%, 50 Hz ±1% three-phase. Low voltage, high voltage, or a lost phase can make the motor overheat or trip. Long or heavily loaded lines can sit outside ±5% at peak hours — measure your real supply, not the nominal one. See our guide on single phase vs three phase borehole pumps for protection advice.
3. Wrong water. The pumps are designed for clean well water: temperature up to 20 °C, solids ≤0.01%, pH 6.5–8.5, chloride ≤400 mg/L, hydrogen sulphide ≤1.5 mg/L. Water outside these limits can wear or corrode the pump early. If your water test exceeds these values, talk to us about suitable options before ordering or reordering.
Prevention Is Cheaper Than Repair
A few habits prevent most failures:
- Always use a proper control panel. It must include short-circuit, phase-loss, and overload protection. This is not optional equipment — it is what protects the motor when the supply misbehaves.
- Check installation limits. First impeller ≥3 m below the dynamic level; the unit not deeper than 70 m below the static level; motor bottom at least 5 m above the well bottom.
- Follow the start procedure. Centrifugal models start with the gate valve closed to about 3/4 of its travel, then open it slowly.
- Keep simple records. Water level, flow, and current once a month. A slow trend can warn you about wear long before a breakdown.
- Size correctly from the start. Many “pump problems” turn out to be selection problems. See how to choose a borehole pump and what size borehole pump do I need before buying.
When the Problem Is the Well, Not the Pump
Not every “pump failure” is a pump failure. A borehole is a living system: the water table can fall in the dry season, screens can clog over the years, and fine sand can move into the well. If your records show the dynamic level falling year after year, or sand appearing where the water was clean before, the well itself may need attention — cleaning, redevelopment, or a different pump setting within the installation limits. Replacing the pump without fixing the well may only buy a few months. When you contact us, share the well history as well as the pump symptoms.
Send Us Your Symptoms
Still stuck? Send us three things: the symptom, the pump model (on the nameplate), and your voltage and current readings if you have them. Photos of the installation and the control panel help too. Our engineers will help you work through the possible causes and discuss whether you need a spare part, a repair, or a new pump. You can also browse the current borehole pump range for replacement models and their duty points.