Boiler frequently loses pressure; you must keep topping up the system.

Safety: Do not repeatedly over‑pressurise the system above the recommended cold pressure (usually 1.0–1.5 bar).

Steps:

• Inspect all visible pipework, radiator valves, and the boiler underside for signs of water leaks or staining.
• Check the PRV discharge pipe (usually copper pipe exiting outside). If it drips when the boiler heats up, the PRV may be passing due to high pressure or debris.
• With the boiler cold, note the pressure. Run heating until hot and check pressure again. If it rises close to or above 3 bar, the expansion vessel may have lost its charge.

Recharging or replacing the expansion vessel and replacing a PRV require a heating engineer. Hidden leaks in floors or walls also need professional investigation.