A backup water tank is only useful if the pump and pressure system behind it actually work. Here are the seven faults we get called out to most often — and how a properly installed system avoids all of them.
1. Pump cycles on and off every few seconds
Cause: failed bladder in the accumulator tank, or no accumulator fitted at all. Without a working accumulator, the pump turns on the instant any tap opens and off the instant it shuts.
Fix: replace the accumulator bladder (R650) or fit a properly-sized accumulator (R2,200). Short-cycling will burn out a pump in under 18 months.
2. Pump runs continuously and never builds pressure
Cause: air in the suction line, foot valve stuck open, or the tank has run dry and the pump is sucking air.
Fix: re-prime the pump, replace the foot valve if it's lost its seal, and fit a low-water cut-off switch in the tank so the pump can't run dry again.
3. Low pressure at upstairs taps
Cause: the pump is undersized for the head and the number of fixtures. A 0.75kW garden pump pressed into service for a two-storey house with 3 bathrooms simply can't deliver.
Fix: replace with a properly-sized 1.1kW or 1.5kW domestic pressure pump matched to bathroom count and head height.
4. Pump trips the earth leakage
Cause: water ingress into the motor seal (common when pumps sit in direct rain), or the pump is wired off a shared circuit with other earth leakage-sensitive equipment.
Fix: dedicated breaker for the pump, dedicated earth leakage, weatherproof pump enclosure.
5. Tank overflows constantly
Cause: failed brass float valve on the municipal inlet, or grit holding the float seat partially open.
Fix: rebuild or replace the float valve and fit a 100-mesh inlet strainer (R450) to keep grit out in future.
6. Water in the house smells of plastic or eggs
Cause: water has sat in a translucent tank in direct sunlight and grown algae or sulphate-reducing bacteria.
Fix: empty and chlorine-shock the tank, fit a UV blanket or move to a dark green tank, install a carbon filter on the outlet.
7. Mains comes back on but the house stays on the tank
Cause: the automatic changeover has stuck (mechanical float type) or the controller has lost its setting (electronic type).
Fix: service or replace the changeover valve. Worth fitting an indicator light or smart monitor so you can see which supply the house is on at a glance.
Prevention beats repair
Most of these faults trace back to an install done by a handyman or DIYed off YouTube. A properly designed system from day one — right pump, right accumulator, dedicated electrical, weatherproof housing, sediment filter, low-water cut-off — will run trouble-free for 10 years.
Pump or backup water issue right now? Phone 082 886 9119 — we service every brand of domestic pressure pump across Sandton and Midrand.