OK so low 'flow' thanks for that, sounds like it is going to be a case of trial and error then by replacing certain parts. Presumably there is a flow switch as well, could this be part of the problem.
OK thanks Boilerman, I suppose there is no way of knowing (unless it's visually obvious) until you replace exchanger if its that or not. Correct in saying hard water area and there is no softner.
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