Richard Weir
Hi Nigel, The hot water system uses heating water from the boiler. There is a diverter valve within the boiler or externally, normally called a 3 port valve, which make this divert of the hot water happen. It sounds like this valve is faulty. If its an external valve located in your airing cupboard then it can easily be replaced. If its inside your boiler then its a little more complicated but still a straight forward job. I would budget £100-£200 to do the job. Hope that helps.
