ISO 21138-1:2020, together with ISO 21138-2 and ISO 21138-3, specifies the definitions and requirements for pipes, fittings and systems based on unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) structured-wall piping systems intended to be used in non-pressure underground drainage and sewerage applications.

NOTE 1 Pipes, fittings and the system complying with this document can also be used for highway drainage and surface water.

This document covers a range of pipe and fitting sizes, materials, pipe constructions, nominal ring stiffnesses, and gives recommendations concerning colours.

NOTE 2 It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account their particular requirements and installation practices or codes.

In conjunction with ISO 21138-2 and ISO 21138-3, this document is applicable to structured-wall pipes and fittings, to their joints and to joints with components of other plastics and non-plastics materials.

It is applicable to structured-wall pipes and fittings with or without an integral socket with elastomeric ring seal joints as well as welded and fused joints.

NOTE 3 Pipes, fittings and other components conforming to any plastics product standards referred to in the Bibliography can be used with pipes and fittings conforming to this document when they conform to the requirements for joint dimensions given in ISO 21138-2 and ISO 21138-3 and to the performance requirements given in Clause 9.

NOTE 4 For dimensions larger than DN/OD 1200 or DN/ID 1200, this document can serve as a general guideline regarding appearance, colour, physical and mechanical characteristics as well as performance requirements.