Boiler frequently loses pressure and needs topping up

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

• Check for visible leaks: Inspect all accessible radiators, valves, and pipework. Look for staining or damp patches.
• Observe relief discharge: Check the pressure relief valve discharge pipe outside for dripping when the boiler is hot. Continuous dripping indicates a fault.
• Monitor pressure pattern: Note how quickly pressure rises when hot and falls when cold. Large swings suggest a failed expansion vessel.
• Professional testing: A technician should test and recharge or replace the ACV expansion vessel and replace a passing relief valve.