Borehole Pump Keeps Tripping? 7 Causes and Fixes

A borehole pump that keeps tripping is telling you something. Resetting it again and again usually ends with a burnt-out motor, so it pays to find the cause. These are the seven we see most often, roughly in order of how common they are.

Safety first: switch off at the isolator before you open any control box. Borehole pumps run on 220V or 380V, so leave electrical tests to a qualified electrician.

1. The pump is running dry

If the pump trips after running for a while and works again after a rest, the water level is probably dropping below the pump. This happens when the pump delivers more than the borehole can supply. A pump should never take more than 70 to 80% of your borehole’s tested yield (see your driller’s report).

Fix: fit a controller that switches the pump off when the water runs low. In our borehole controllers range, the 20Y intelligent controllers give 220V pumps dry-run, over- and under-voltage and overload protection with automatic restart, and the Y1 digital controllers protect 380V three-phase pumps against dry running, phase loss and bad voltage. A basic analogue control box does not switch the pump off when the borehole runs dry. If the pump is simply too big for the borehole, a smaller pump is the long-term answer: our borehole pump size guide shows how to match a pump to your yield.

2. Sand or silt has jammed the pump

Sand wears the impellers and can lock the pump solid, so the motor draws too much current and the overload trips straight away. Sandy water at the taps is a clear warning sign.

Fix: the pump has to come out to be cleaned or rebuilt. When it goes back in, hang it a few metres above the bottom of the hole so it doesn’t suck up sand. Power monitoring such as the NIST Motorscope stops the motor as soon as its power draw moves outside safe limits, before a jam burns it out.

3. The cable is too thin for the distance

A long cable that is too thin causes voltage drop. The motor then runs on low voltage, draws more current, overheats and trips, often on hot afternoons.

Fix: check your cable against our cable sizing chart for the motor size and the full distance from the board to the pump.

4. Low or unstable supply voltage

Low voltage, generators and the power surge when electricity returns after load shedding all stress a borehole motor. If tripping started around power problems, this is the likely cause.

Fix: ask an electrician to measure the voltage at the control box while the pump runs, and fit a controller with over- and under-voltage protection, such as the 20Y (220V) or Y1 (380V) from our borehole controllers range.

5. A failed capacitor or control box

Single-phase borehole pumps rely on a capacitor in the control box. When it fails, the motor hums but doesn’t start, gets hot and trips.

Fix: an electrician can test and replace the capacitor or the control box. It is a cheap repair if it’s caught before the motor burns out.

6. The earth leakage trips

If the earth leakage trips rather than the pump’s breaker, current is escaping, usually through a damaged cable or a cable joint that has let water in down the borehole.

Fix: an electrician tests the cable and motor insulation. A leaking joint must be redone with a proper waterproof cable joint kit; a damaged motor may need replacing from our borehole motors.

7. The pump starts and stops too often

Every start heats the motor. If your pump switches on every time someone opens a tap, the pressure tank has probably lost its air charge or its bladder has burst, and the motor eventually overheats.

Fix: check the tank’s pre-charge pressure and replace a burst bladder or tank.

Frequently asked questions

Why does my borehole pump trip after running for a while?

Most often the borehole is running dry or the motor is overheating from voltage drop. Watch whether the water flow weakens before it trips: that points to running dry.

Why does my borehole pump trip the earth leakage?

Current is leaking to earth, usually through a damaged cable or a cable joint that has taken in water. Have an electrician test the insulation before resetting it again.

Can load shedding damage my borehole pump?

Repeated power cuts, low voltage and surges when the power returns all shorten a motor’s life. Good pump protection pays for itself.

How do I stop my borehole from running dry?

Size the pump to no more than 70 to 80% of the tested yield and fit a controller with dry-run protection. A storage tank helps too: a smaller pump can then run for longer at a rate the borehole can keep up with.

Need a replacement or a second opinion?

Send us your driller’s report, the pump and motor details and the cable length on WhatsApp 012 881 1962. We’ll help you find the cause and size the right replacement, with delivery anywhere in South Africa. Browse all borehole pumps.