Boiler makes gurgling noises, especially at startup or shutdown

Safety: Some gurgling from condensate is normal, but loud or persistent noises should be checked.

• Bleed radiators: Remove air from all radiators, starting with those upstairs, then re-pressurise the system.
• Check system pressure: Maintain 1.0–1.5 bar cold.
• Listen to condensate trap: Gentle gurgling near the bottom of the boiler can be normal. If very loud, the trap may be partially blocked and should be cleaned by an engineer.
• Engineer actions: The engineer will bleed the boiler's internal air vents, clean the condensate trap, and verify correct system filling.