This Part of EN 1401 specifies the requirements for pipes, fittings and the system of unplasticized poly(vinyl chloride) (PVC-U) piping systems in the field of non-pressure underground drainage and sewerage outside the building structure (application area code "U") and both buried in ground within the building structure (application area code "D") and outside the building. This is reflected in the marking of products by "U" and "UD". It also specifies the test parameters for the test methods referred to in this European Standard. This European Standard covers a range of nominal sizes, a range of pipes and fittings series and a range of stiffness classes and gives recommendations concerning colours. NOTE 1 It is the responsibility of the purchaser or specifier to make the appropriate selection from these aspects, taking into account their particular requirements and any relevant national regulations and installation practices or codes. In conjunction with prCEN/TS 1401-2 [1] and ENV 1401-3 [2] it is applicable to PVC-U pipes and fittings, their joints and to joints with components of other plastics and non-plastics materials intended to be used for buried piping systems for non-pressure underground drainage and sewerage. This European Standard is applicable to PVC-U pipes without a socket as well as pipes with an integral socket. The pipes can be manufactured by extrusion (see 3.3 monolayer pipe) or by co-extrusion (see 3.4 multilayer pipe). The fittings can be manufactured by injection-moulding or be fabricated from pipes and/or mouldings. Requirements and limiting values for application area code "D" are given in Table 4, Table 6, Table 13 and Table 15. NOTE 2 Pipes, fittings and other components conforming to any of the plastics product standards listed in Annex C can be used with pipes and fittings conforming to this European Standard, provided they conform to the requirements for joint dimensions given in Clause 6 and to the requirements of Table 15.