"peter wrote in
:

Thanks for the suggestion, everything is obvious isn't it when someone
tells you. Slight problem, stopcock feeding hot water cylinder is
stuck, looks very old and not used in years. Not sure what will happen
if I apply some force to it ,to try and free it. I assume I can
achieve the same by emptying the cold water tank


And, while you're at it, replace it with a full bore lever ball valve

mike