How to Fix / Troubleshooting

Safety: Do not repeatedly overfill the system above the recommended pressure.

Visual leak check: Inspect all radiators, valves, and visible pipework for damp patches or staining.
Check safety valve outlet: Look at the discharge pipe outside; if it is wet or dripping, the safety valve may be passing.
Expansion vessel test (technician):
- Isolate and drain pressure from the boiler.
- Measure the air charge at the expansion vessel Schrader valve; recharge to the value specified by Junkers if low.
- Replace the expansion vessel if the diaphragm has failed.
System pressure monitoring: Mark the gauge and monitor over several days to locate intermittent losses.

Boiler frequently loses pressure and needs topping up

Possible Causes