Worcester 28i Combi boiler keeps loosing pressure?

Pressure loss is always caused by a leak. If there is no evidence of water then first thing to try is pressurise boiler to about 2 bar and turn on the heating. If the pressure gauge rises too much (above 3 bar) the boiler will discharge water through the presure relief valve (usually a 15mm pipe which points outside). If this occurs then the expansion vessel in the boiler will need to be re-charged with air or replaced if the diaphragm is burst. The pipe leadinding to the expansion vessel may also be blocked. Otherwise i'd be checking under the floor and the heating drain point for a leak.

Ian
July 2009