DSD Polyethylene Outside Diameter (OD) conversion to Nominal Diameter (DN)

The Hong Kong Drainage Services Department (DSD) publishes a conversion table in Appendix 5A, to ensure proper ID alignment when connecting Polyethylene pipes with other pipe materials used in its pressure and drainage network.

PE pipe size is defined by its outside diameter (DN/OD for pipes and dn for fittings), whereas Ductile Iron, Reinforced Concrete, Earthenware and other wastewater pipe materials are defined by their nominal Bore (DN).

It should be noted that PE pipes internal dimension varies depending on the pipes wall thickness (SN / SDR Rating). The table below provides the official DSD PE OD to DN conversions, as given in DSD PS Appendix 5A, for both pressure and gravity drainage. DSD Appendix 5A

Note: Larger sizes are not stipulated in Appendix 5A, but are available up to DN/OD 2800 in PN8 SDR21.

Page from DSD Appendix 5A for reference.

Page from DSD Specification for Gravity Sewer and Stormwater Drain Connection for Reference