This part is based near the water pipework. The water pipework can be split in to 2 categories. The first would be the pipes that allow water to be fed in to the heating unit. This would include the mains water supply and the water pipework on the wall jig. The second category would be the pipes within the appliance that carry water to, from and between the numerous mechanisms of the unit that require it, such as the pump and diverter valve .