7641 Mechanical piping (0) Piping, valves, fittings and accessories associated with mechanical systems including; chilled, condenser and heating water, and other fluids and gases 7642 Mechanical piping insulation (7) Insulation and sheathing of piping, tanks, vessels and flues 7643 Water treatment (0) Water treatment for mechanical systems, open and closed water systems 7645 Liquid fuels (0) Design and installation of a Diesel (usually) fuel installation, including, storage tanks - above and below ground, service tanks, piping, fuel pumps. Components and accessories when supplied as part of the system.