Hi all
thanks for your replies and on further in spection I fear I have a blockage as I’m only getting water from one drain off valve that being the one at the highest point, the system has no radiators but has a pump I think the way may be to flush the system as suggested by mike the boiler man unfortunately there seem to be no drain offs on the lower pipe work so I may have to disconnect both pipes going into the back boiler and flush from there.
Ant further suggestions greatly received, and thanks for all replies so far.
I’ll keep you all posted with updates.
regards paul