Not too difficult for yourself then I would think. Be prepared and have the Installation and Servicing manual with you and go to replacement of parts section, it will guide you through it step by step, hopefully with diagrams. Also I wouldn't do it without a spare set of fibre washers or 'o' rings, you run the risk of a leak if you re-use the old ones, clean the brass surfaces before fitting them with an abrasive pad to get rough bits of old washers off. Some diverter valves come with the washers in the box, I can't remember if Baxi do supply with this model, if not, order a service kit of washers for the boiler. Best of luck.
Taliskerman, June 2011
