On Thu, 29 May 2008 14:28:04 +0100, Roger Mills wrote:

[1] There are degrees of shottedness - some of which are fixable just by
topping up the air through the schrader valve, and some of which are not
without replacing the whole thing

Or more practicably by adding a new one externally, in the many cases where
you'd have to virtually dismantle the boiler to get at the one built-in.

--
John Stumbles

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh