DS EN 253:2009 District Heating Pipes - Preinsulated Bonded Pipe Systems For Directly Buried Hot Water Networks - Pipe Assembly Of Steel Service Pipe, Polyurethane Thermal Insulation And Outer Casing Of Polyethylene Defines requirements and test methods for straight lengths of prefabricated thermally insulated pipe-in-pipe assemblies for directly buried hot water networks, comprising a steel service pipe from DN