On Sun, 15 Oct 2006 17:23:55 +0100, Andy Hall
wrote:

Thanks for the reply. It just occurred to me: scaling is only likely
to occur on the side of the heat exchanger that passes water from the
mains inlet to the sink taps, isn't it? In if that side was scaled up,
then there would be a reduction in flow from the hot taps, wouldn't
there?

Jim D

Possibly some, yes.

If the system is sludged, then a different course of action is needed -
basically clean it out and fill adding corrosion inhibitor to the
system afterwards

That's exactly what I did, a few days ago, just before this problem
started..

Jim D