Combined Pipe Specifications The inbuilt pipework database contains certain selections which are a combination of materials: Steel, 1387 Heavy/3600: Pipes up to and including 150mm dia (6") are EN 10255/BS1387 'Heavy' sizes; 200mm dia (8") and above are EN 10220/BS3600 sizes. Schedule 40/STD: Pipes up to and including 200mm dia (8") are Schedule 40 sizes; 250mm dia (10") and above are STD sizes. Typical Pipe Materials The inbuilt pipework database contains certain selections which have typical dimensions that should be treated as being preliminary, subject to confirmation by the manufacturer: BS EN 10220 (ex BS3600) Typical: Nominal and outside diameters are based upon standard dimensions given by EN 10220/BS3600, with wall thickness incrementing up to the maximum of 25mm (1in) given in the standard.