how can i fix my worcester combi 350 boiler?

When you bleed any water out of the system, the water pressure inside the boiler will drop. With the boiler off, open the water filling loop valve until you have a pressure of about 1 bar. When the system is running, expect a small pressure increase but when the boiler shuts down the pressure should drop again. Don't overfill the boiler though - you'll have to remove more water if you do.

John
December 2007