Quick answer
Short-cycling — the pump snapping on and off rapidly whenever a tap is opened — is almost always a waterlogged bladder tank or a pressure switch out of calibration. The bladder holds an air cushion that lets the pump deliver a reservoir of pressurised water between cycles. When that air is lost, there is nothing to buffer demand and the pump switches on the moment anything is drawn.
Common causes
- Waterlogged bladder tank that has lost its air charge
- Pressure switch out of calibration or with worn contacts
- Ruptured bladder inside the pressure vessel
- Undersized pressure vessel for the pump and the household demand
- Non-return valve leaking back and dropping outlet pressure between draws
What you can do now
- 1Note how many times it cycles when you open one tap — more than a few is clearly short-cycling
- 2Check whether the pressure vessel feels completely full and heavy, which indicates waterlogging
- 3Listen for the switch clicking rapidly, which points at the switch rather than the vessel
- 4Switch the pump off between uses if it is cycling badly, to protect the motor
- 5Do not attempt to re-charge the bladder yourself — it must be done with the system depressurised
When to call a professional
Book within the week. Short-cycling destroys pump motors and switches quickly, and a technician can usually re-pressurise the bladder to just below the cut-in pressure or replace the vessel for far less than a new pump. If the bladder has ruptured, the vessel needs replacing rather than recharging, and a correctly sized one will stop it recurring.
Typical cost in Johannesburg
Bladder service R650 · Switch R650
Indicative ranges only. We provide written, itemised quotes before any work.
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