In message , altheman
writes
hi, thanks for the speedy response....i am not sure if i have gravity hw or
all pumped..the set up is as follows....i have in the loft a main tank...and
a header tank....and also in the airing cupboard there is a big tank that
actually holds the hot water...not sure if that is the type of information
that will help...but personnaly i have no ideas about central
heating..sorry...thanks again


Just try it and see then ...

Did you not think to play with it a bit before it suddenly became an
urgent problem ?


--
geoff