On 05/12/2011 15:11, Lieutenant Scott wrote:

Of course. Do you mean to tell me that the large bore systems don't
have a correspondingly larger bore pipe from the boiler to feed them?
What ****t designed that?!?

You don't get large bore domestic heating systems these days. 1", 3/4"
and 1/2" pipes were traditionally known as small bore which is why the
smaller stuff got labelled micro-bore.
--
Roger Chapman