A water pump can lose pressure without a visible leak because water is flowing backwards through a faulty check valve or foot valve, the pressure tank is waterlogged or incorrectly charged, or air is entering the suction line. Restrictions, low source-water level, loss of prime, worn pump parts or faulty controls can also cause low pressure. A concealed leak remains possible. If the pressure rises and falls rather than steadily dropping, compare the causes of fluctuating water pressure.
What the pump’s behaviour indicates
- Pressure falls with all outlets closed: The pump may not be holding pressure because of internal backflow through a check valve or foot valve. A concealed leak is another possibility.
- The pump cycles rapidly during use: The pressure tank may have an incorrect air charge, a damaged bladder or insufficient air space. The pump then reaches its start and stop pressures too quickly.
- Pressure is weak only while water is running: Look for an accessible blocked filter, partly closed valve, restricted pipework, low source-water level or a worn pump component. These faults limit flow rather than releasing stored pressure. If only hot outlets are affected, investigate the causes of low hot-water pressure instead.
- Water splutters or the pump loses prime: Air may be entering through a suction-side connection. Because the suction line can operate below atmospheric pressure, it may draw in air without leaking water out.
- The pump does not start or stop normally: The pressure switch, electronic controller or electrical supply may be faulty.
These symptoms narrow down the likely fault but do not confirm which component has failed.
Safe preliminary checks
- Turn off all taps, irrigation outlets and water-using appliances. Observe whether the pressure gauge falls or the pump starts by itself.
- Check from a safe location that the rainwater tank, bore or other source has enough water. Never enter a tank or confined space.
- Confirm accessible isolation valves are fully open. Look for visible pipe damage, water around the pump or obviously loose connections.
- Inspect or clean only filters identified as user-serviceable by the manufacturer. Isolate the pump and release system pressure exactly as instructed before opening any housing.
Do not remove electrical covers, adjust controls, dismantle the pump or open a pressure tank. Pressure-tank checks require electrical isolation, complete pressure release and the manufacturer’s procedure; there is no universal air-charge setting. Follow the limits on safe household pressure checks and leave electrical diagnosis to an appropriately licensed electrician or qualified pump technician.
If pressure keeps falling with every outlet closed, the pump repeatedly cycles or it continues losing prime, contact our water pressure plumbers. They can assess the accessible pipework, tank and valves and coordinate specialist electrical testing where required.