I have a Glow Worm Energysaver 50e boiler which has started dripping from just below the burner. Water pipes seem to be ok and there is nothing obvious inside. When I take the burner cover off and dry it out after a few minutes it is slightly damp again without any obvious source. Underneath the burner there is a chamber with what appears to be a vent in the side. This seems to have water sitting in it up to its edge. What is this?