In article ,
"neverwas" writes:
What surprised me was that the stuff I've looked at for
(among others) Worcester and Vaillant boilers still just say
in both user and technical literature (to take one example):
"The temperature in the domestic hot water heat exchanger is
limited by the boiler control system and it is not necessary
to install a scale reducer on the cold mains to the boiler.
However, in areas that get exceptionally hard water, a scale
reducer may be fitted to prevent scale formation in the hot
water system pipes."

I had an old Main Medina multi-point water heater when I moved
in to a house many years ago. I had to take the heat exchanger
out of that and clean it about every 2 years. The multi-point
was replaced in 2000 and the new model claims teflon coating
on the inside of the heat exchanger pipework to prevent scale.
It seems to work -- I've never had to descale it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]