Pressure Pump Not Switching On? A Troubleshooting Guide for Tank Systems

Your taps are dry, the tank is sitting there full of water, and the pump is completely silent. Before you reach for the phone, a methodical check through the most common causes will save you time, money, and the frustration of a call-out fee for something you could have sorted yourself. This guide walks through each failure point in a logical order — start at the top and work down.

1. Check Power First — Every Time

It sounds obvious, but the most common reason a pressure pump does nothing at all is a tripped circuit breaker or a blown fuse. Go to your distribution board and look for any tripped breaker — it will be sitting in the middle position rather than fully on or fully off. Reset it firmly: off first, then back on.

If the breaker trips again immediately, stop. A breaker that trips on reset suggests an electrical fault in the pump motor or wiring, and that is a job for a qualified electrician. Electrical work on pumps falls under the Occupational Health and Safety Act administered by the Department of Employment and Labour; wiring a pump system without the correct certification is not just risky, it can void your insurance.

Also check:

• The isolator switch next to the pump itself — these are sometimes knocked off accidentally.
• Any GFCI (earth-leakage) outlet if the pump is plugged into one rather than hard-wired.
• The controller’s own power indicator light if your system has a separate controller box.

2. Is the Tank Actually Empty, or Is the Float Switch Lying?

Dry-run protection exists to stop a pump burning itself out by running without water. If the tank level drops below the sensor threshold — or if a float switch is stuck — the pump cuts out and will not restart until the condition clears.

Open the tank and check the actual water level with your own eyes. If the tank is empty, refill it from your municipal supply or wait for the delivery line to fill it, then try the pump again. If the tank has water but the pump still won’t start, the level sensor or float switch itself may have failed in the “low” position, incorrectly telling the controller the tank is dry.

A stuck float is easy to diagnose: reach in (with power isolated) and move the float arm manually through its full range. If it feels stiff or doesn’t spring back, that is your culprit. Replacement floats are inexpensive and widely available.

For a broader look at how tank-and-pump backup systems are configured and what components interact with each other, the backup water systems guide is a useful reference.

3. The Pressure Switch: The Most Misunderstood Component

The pressure switch monitors system pressure and tells the pump when to start (low pressure) and stop (target pressure reached). When it fails, sticks, or is set incorrectly, the pump behaves as if there is no demand — even when your taps are wide open.

Locate the pressure switch — it is usually a small grey or black box screwed into the pump outlet line. There are two common faults:

Contacts welded shut or burnt open. Unscrew the cover (with power off) and look for pitting, discolouration or visible arcing on the contacts. Burnt contacts mean the switch needs replacement, not adjustment.

Cut-in and cut-out pressures set wrong. Pressure switches have two springs inside: one sets the cut-in pressure (when the pump starts) and one sets the differential (how far pressure must rise before it stops). If someone adjusted these incorrectly — or if they drifted — the switch may never signal the pump to start. Adjusting these settings correctly requires a pressure gauge on the system and a working knowledge of the pump’s rated pressures; if you are unsure, a technician should do this.

If you have already replaced a switch and are still seeing problems with low output rather than complete silence, read through low water pressure from a tank system for a more detailed diagnosis of pressure-side faults.

4. Capacitor and Motor Faults

Single-phase pump motors use a start capacitor (and sometimes a run capacitor) to generate the phase shift that gets the motor spinning. A failed capacitor is one of the most common reasons a pump hums but does not turn — or makes no sound at all.

Signs of a dead capacitor:

• The pump hums briefly then cuts out on overload protection.
• The motor is warm to the touch even though it hasn’t run.
• You can hear a faint click from the contactor but no rotation.

Capacitors can store a dangerous charge even when power is disconnected. Do not attempt to test or replace one unless you know how to discharge it safely. This is a straightforward repair for an electrician or pump technician and typically takes under an hour.

If the motor itself has seized — usually from running dry — you will hear nothing, and the shaft won’t turn by hand (with power off and the coupling exposed). Seized motors generally need rewinding or replacement.

If the fault turns out to need professional hands, getting competitive quotes makes sense before committing to one installer. Compare 3 free quotes — vetted installers, no obligation.

5. Controller and Automation Faults

Many modern tank systems use a dedicated pump controller — a small electronic unit that manages dry-run protection, restart delays, and sometimes remote monitoring. These units add useful features but also add a potential failure point.

Common controller issues:

• Lockout after a fault: Most controllers lock out the pump after repeated dry-run trips and require a manual reset. Check the display or indicator LEDs for a fault code and consult the manual for the reset procedure.
• Delay timers: Some controllers impose a restart delay of 30 seconds to several minutes after the pump stops. If you are testing the pump repeatedly in quick succession, you may simply be hitting that delay.
• Sensor wiring: The controller relies on the tank sensor sending accurate signals. A corroded or loose sensor wire produces the same symptom as an empty tank.

If your controller is more than five years old and showing erratic behaviour, replacement is often more cost-effective than repeated repairs — though a technician should confirm this after inspection.

6. When to Call a Professional — and What to Expect

If you have worked through power, tank level, the float switch, the pressure switch and a capacitor check without finding the fault, or if any step involves electrical work beyond resetting a breaker, it is time to call a qualified installer or pump technician.

Before the technician arrives:

• Write down what the pump does (hums, clicks, nothing at all, trips breaker) and when it started.
• Note any recent events — a power surge, a period of running the tank dry, any recent work on the system.
• Check whether the pump is still under its manufacturer warranty and whether the installer offered a workmanship guarantee.

For guidance on what a reasonable after-sales response looks like and what you are entitled to expect from an installer, after-sales service expectations sets out the key points clearly.

For reference, borehole pump systems in Johannesburg typically cost R40,000–R150,000 fully installed, with most falling between R60,000 and R100,000; tank-and-pump backup systems typically run R20,000–R40,000, with whole-house configurations around R55,000. These are Johannesburg reference points — costs vary by region, site conditions and specification, so confirm via quotes for your area. If your pump is several years old and the repair quote approaches half the replacement cost, it is worth asking the technician to quote both options.

Also worth knowing: if you suspect a borehole pump that’s stopped working rather than a tank pressure pump, the fault sequence is similar in places but the components differ — that guide covers the borehole-specific checks.

If a repair or full system replacement is on the cards, comparing installer prices is the fastest way to avoid overpaying. Get 3 installer quotes free — no obligation, no pressure.

Keeping the Pump Reliable Long-Term

Most pressure pump failures are preventable with basic maintenance:

Maintenance task	Suggested frequency
Check and clean inlet strainer/filter	Every 3–6 months
Inspect pressure switch contacts	Annually
Test dry-run protection manually	Annually
Check capacitor condition (technician)	Every 2–3 years
Inspect all wiring connections	Annually

The South African Bureau of Standards (SABS) publishes standards relevant to pump and water system installations; SANS 241 (2024 edition) covers drinking-water quality where treated water is involved. Any electrical installation or modification must comply with the Occupational Health and Safety Act requirements administered by the Department of Employment and Labour, which means work must be carried out by or under the supervision of a registered electrician.

A pump that is correctly installed, regularly maintained, and matched to the actual flow and pressure demands of the house will outlast one that was oversized, undersized, or left to run to failure. When you do eventually need a replacement or an upgrade, getting at least three quotes from vetted installers remains the simplest way to ensure you are paying a fair price for the right equipment.