On Fri, 31 Aug 2012 14:48:17 +0100, Tim+ wrote:
What I want to know is, where the feck is all this crud hiding??

Are you sure the bottom of the tank's not scaled up, with the crap hiding
on top (and the scale acting as a filter when you use the drain tap)? I
attacked ours a couple of years ago after performance started dropping
off, and probably the bottom ten inches or so of the tank was full of
scale.