This Technical Specification, together with ENV 1046 and EN 1610, provides a material-specific set of guidelines for the installation of piping systems made of polypropylene (PP) in the field of non-pressure underground drainage and sewerage. - outside the building structure (application area code "U"); - 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".