my glow worm ultimate bolier 40ff does it refill auto when i replace a?

I have the same and yes it does. Mine appears to get it directly from the header tank in my loft. When I drain water from the system (i.e. to replace a radiator) the header started refilling so I knew the system worked correctly. To change radiator you will need to turn the water off the drain the system. Hope this helps.

Simon
March 2008