Water feed inlet is getting into the central heating system?

The Main cold water feed that feeds the hotwater is getting mixed with the central heating system. Can you tell me what the problem might be. I have a Sime friendly format 80 e boiler.
Mr Etto, March 2005


done
Could be the heat exchanger in the boiler is cracked or it could be that the hot water cylinder is faulty.

plumbob, March 2005
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