Standard of the International Organization for Standardization (ISO) that defines the requirements and test methods applicable to ductile iron pipes, fittings, accessories and their joints for the construction of pipelines

The following is the text that appears in the ISO standard web site:
ISO 2531:2009 specifies the requirements and test methods applicable to ductile iron pipes, fittings, accessories and their joints for the construction of pipelines:

- to convey water (e.g. for human consumption and raw water),

- operated with or without pressure, and

- installed below or above ground.

It specifies materials, dimensions and tolerances, mechanical properties and standard coatings of pipes, fittings and accessories. It also gives performance requirements for all components including joints.

ISO 2531:2009 applies to pipes, fittings and accessories cast by any type of foundry process or manufactured by fabrication of cast components, as well as corresponding joints in the size range DN 40 to DN 2600 inclusive.

The page on the ISO site where you can purchase the standard https://www.iso.org/standard/40396.html