Séan Connolly wrote:
Too big for gas - could it have been the feed/return to
the cylinder?

Not sure what you mean ?

The hot water cylinder.


Sorry my knowledge on these matters is pretty limited, I didn't understand
what you ment by feed/return.


In many older systems where gravity fed primaries were used, it was
common to use 28mm pipe between the boiler and the hot water cylinder.