In article ,
JimD writes:
I can buy yet another heat exchanger tomorrow, but is ther anything
else I should be doing to prolong its life? Water filter, perhaps?

I don't know this model, but why not descale it?

I descalled a friend's one from a Baxi using Furnox DS-3.
Dissolve some DS-3 in a large jug of hot water.
Stand the heat exchanger in a washing up bowl to catch
the descaller, and pour into the hot water side of the
heat exchanger slowly. Be prepared for violent descalling
spitting out the acid and acid spray. When you've poured
it all through, empty the heat exchanger out into the bowl,
transfer back to the jug, and the pour through again, until
the heat exchanger stops fizzing. If the descaller goes blue,
it's used up -- discard and mix up some fresh.

DS-3 is available from a plumber's merchant, and possibly
larger B&Q's. I'm assuming the heat exchanger is stainless
steel -- if it's something else, check compatibility with
the DS-3.

DS-3 is sulphamic acid, i.e. pure kettle descaller without
the sand and other rubbish you find mixed in with retail
kettle descallers to dilute them. It has an indicator added
so you can tell it's used up by change of colour, and a smell
so you don't accidently drink it. A tub of it can be useful
for other things too, but don't use it on plastic parts (or
plastic kettles), as it can make them brittle.

--
Andrew Gabriel