Boiler shows 109, pressure rises quickly when heating, water discharges from safety valve

Safety: Hot water may discharge from the safety valve pipe; keep clear of discharge point.

• Check pressure cold: When the system is cold, note the pressure. It should be around 1.0–1.5 bar. If above 2.0 bar, the system is overfilled.
• Reduce pressure: Bleed water from a radiator using a bleed key into a container until the pressure drops to about 1.2 bar.
• Inspect filling loop: Ensure the filling loop valves are fully closed and the flexible hose is removed if external. A passing valve can slowly overfill the system.
• Expansion vessel test: If pressure rises above 3 bar when hot and the safety valve discharges, the expansion vessel may have lost air charge. A professional can check and recharge via the Schrader valve or replace the vessel.
• Safety valve: Once a pressure relief valve has discharged, it may not reseal properly and can drip. Replacement by an engineer is recommended.