Boiler frequently loses pressure over days or weeks without visible leaks

Safety first: Repeatedly topping up introduces fresh oxygen, increasing corrosion. Do not ignore ongoing pressure loss.

• Check discharge pipe: Look at the external copper safety discharge pipe for signs of dripping or staining, indicating a passing relief valve.
• Inspect radiators and valves: Look for small rust marks or damp patches around valve spindles and joints.
• Record pressure changes: Note cold and hot pressures over several days to help the technician diagnose.
• Technician test: A Nibe technician will isolate and test the expansion vessel pre-charge and replace the Nibe expansion vessel or pressure relief valve if faulty.