On 03/11/18 17:50, DerbyBorn wrote:
After lots of checking a Heating Engineer has decided a mate's heating
system has a partly blocked boiler heat exchanger. Likely? 12 - 15 years
old. Has been pressure cleaned a couple of years ago.


Quite possible in that timescale - the heat exchanger sees mains water
all the time, so hard water will scale it up.

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